Honor CMAKE_<LANG>_FLAGS[_<CONFIG>]_INIT set in toolchain files

Document these variables.

Change our convention for setting these variables from:

    set(CMAKE_C_FLAGS_INIT "...")

to

    string(APPEND CMAKE_C_FLAGS_INIT " ...")

so that any value previously set by a toolchain file will be used.

Automate the conversion with:

    sed -i 's/set *(\(CMAKE_\(C\|CXX\|Fortran\|RC\|ASM\|${[^}]\+}\)_FLAGS\(_[^_]\+\)\?_INIT \+"\)/string(APPEND \1 /' \
      Modules/Compiler/*.cmake Modules/Platform/*.cmake

and follow up with some manual fixes (e.g. to cases that already
meant to append).  Also revert the automated changes to contexts
that are not protected from running multiple times.

36 files changed, 149 insertions, 149 deletions

diff --git a/Modules/Compiler/ARMCC.cmake b/Modules/Compiler/ARMCC.cmake
index 3cf628c0d0..2ec75c337a 100644
--- a/Modules/Compiler/ARMCC.cmake
+++ b/Modules/Compiler/ARMCC.cmake
@@ -20,11 +20,11 @@ set(CMAKE_AR "${CMAKE_ARMCC_AR}" CACHE FILEPATH "The ARMCC archiver" FORCE)
 mark_as_advanced(CMAKE_ARMCC_AR)
 
 macro(__compiler_armcc lang)
-  set(CMAKE_${lang}_FLAGS_INIT "")
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-Ospace -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-Otime -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -Ospace -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -Otime -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -O2 -g")
 
   set(CMAKE_${lang}_OUTPUT_EXTENSION ".o")
   set(CMAKE_${lang}_OUTPUT_EXTENSION_REPLACE 1)
diff --git a/Modules/Compiler/Absoft-Fortran.cmake b/Modules/Compiler/Absoft-Fortran.cmake
index 2e1666fbf1..da1fc80d41 100644
--- a/Modules/Compiler/Absoft-Fortran.cmake
+++ b/Modules/Compiler/Absoft-Fortran.cmake
@@ -1,8 +1,8 @@
-set(CMAKE_Fortran_FLAGS_INIT "")
-set(CMAKE_Fortran_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "")
-set(CMAKE_Fortran_FLAGS_RELEASE_INIT "-O3")
-set(CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " ")
+string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_Fortran_FLAGS_MINSIZEREL_INIT " ")
+string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " -O3")
+string(APPEND CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT " -O2 -g")
 set(CMAKE_Fortran_MODDIR_FLAG "-YMOD_OUT_DIR=")
 set(CMAKE_Fortran_MODPATH_FLAG "-p")
 set(CMAKE_Fortran_VERBOSE_FLAG "-v")
diff --git a/Modules/Compiler/Bruce-C.cmake b/Modules/Compiler/Bruce-C.cmake
index 23676eccba..cfabe6523a 100644
--- a/Modules/Compiler/Bruce-C.cmake
+++ b/Modules/Compiler/Bruce-C.cmake
@@ -1,7 +1,7 @@
 # Bruce C Compiler ignores "-g" flag and optimization cannot be
 # enabled here (it is implemented only for 8086 target).
-set (CMAKE_C_FLAGS_INIT "-D__CLASSIC_C__")
-set (CMAKE_C_FLAGS_DEBUG_INIT "-g")
-set (CMAKE_C_FLAGS_MINSIZEREL_INIT "-DNDEBUG")
-set (CMAKE_C_FLAGS_RELEASE_INIT "-DNDEBUG")
-set (CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-g -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_INIT " -D__CLASSIC_C__")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -g -DNDEBUG")
diff --git a/Modules/Compiler/G95-Fortran.cmake b/Modules/Compiler/G95-Fortran.cmake
index fd84848b43..2c83fb8fce 100644
--- a/Modules/Compiler/G95-Fortran.cmake
+++ b/Modules/Compiler/G95-Fortran.cmake
@@ -1,8 +1,8 @@
-set(CMAKE_Fortran_FLAGS_INIT "")
-set(CMAKE_Fortran_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "-Os")
-set(CMAKE_Fortran_FLAGS_RELEASE_INIT "-O3")
-set(CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " ")
+string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_Fortran_FLAGS_MINSIZEREL_INIT " -Os")
+string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " -O3")
+string(APPEND CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT " -O2 -g")
 set(CMAKE_Fortran_MODDIR_FLAG "-fmod=")
 set(CMAKE_Fortran_VERBOSE_FLAG "-v")
 set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-ffixed-form")
diff --git a/Modules/Compiler/GHS-C.cmake b/Modules/Compiler/GHS-C.cmake
index 3072715def..c30bdecaf0 100644
--- a/Modules/Compiler/GHS-C.cmake
+++ b/Modules/Compiler/GHS-C.cmake
@@ -3,11 +3,11 @@ include(Compiler/GHS)
 set(CMAKE_C_VERBOSE_FLAG "-v")
 set(CMAKE_C_OUTPUT_EXTENSION ".o")
 
-set(CMAKE_C_FLAGS_INIT "")
-set(CMAKE_C_FLAGS_DEBUG_INIT "-Odebug -g")
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "-Ospace")
-set(CMAKE_C_FLAGS_RELEASE_INIT "-O")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-O -g")
+string(APPEND CMAKE_C_FLAGS_INIT " ")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " -Odebug -g")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -Ospace")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -O")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -O -g")
 
 set(CMAKE_C_GHS_KERNEL_FLAGS_DEBUG_INIT "-ldebug ${CMAKE_C_FLAGS_DEBUG_INIT}")
 set(CMAKE_C_GHS_KERNEL_FLAGS_MINSIZEREL_INIT "${CMAKE_C_FLAGS_MINSIZEREL_INIT}")
diff --git a/Modules/Compiler/GHS-CXX.cmake b/Modules/Compiler/GHS-CXX.cmake
index a51591b2a4..b3018a7b66 100644
--- a/Modules/Compiler/GHS-CXX.cmake
+++ b/Modules/Compiler/GHS-CXX.cmake
@@ -3,11 +3,11 @@ include(Compiler/GHS)
 set(CMAKE_CXX_VERBOSE_FLAG "-v")
 set(CMAKE_CXX_OUTPUT_EXTENSION ".o")
 
-set(CMAKE_CXX_FLAGS_INIT "")
-set(CMAKE_CXX_FLAGS_DEBUG_INIT "-Odebug -g")
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "-Ospace")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "-O")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-O -g")
+string(APPEND CMAKE_CXX_FLAGS_INIT " ")
+string(APPEND CMAKE_CXX_FLAGS_DEBUG_INIT " -Odebug -g")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -Ospace")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -O")
+string(APPEND CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT " -O -g")
 
 set(CMAKE_CXX_GHS_KERNEL_FLAGS_DEBUG_INIT
   "-ldebug ${CMAKE_CXX_FLAGS_DEBUG_INIT}")
diff --git a/Modules/Compiler/GNU-Fortran.cmake b/Modules/Compiler/GNU-Fortran.cmake
index e9c8a594ab..fc848ac42b 100644
--- a/Modules/Compiler/GNU-Fortran.cmake
+++ b/Modules/Compiler/GNU-Fortran.cmake
@@ -5,8 +5,8 @@ set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-ffixed-form")
 set(CMAKE_Fortran_FORMAT_FREE_FLAG "-ffree-form")
 
 # No -DNDEBUG for Fortran.
-set(CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "-Os")
-set(CMAKE_Fortran_FLAGS_RELEASE_INIT "-O3")
+string(APPEND CMAKE_Fortran_FLAGS_MINSIZEREL_INIT " -Os")
+string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " -O3")
 
 # No -isystem for Fortran because it will not find .mod files.
 unset(CMAKE_INCLUDE_SYSTEM_FLAG_Fortran)
diff --git a/Modules/Compiler/GNU.cmake b/Modules/Compiler/GNU.cmake
index c2d393dc81..34d4eafc25 100644
--- a/Modules/Compiler/GNU.cmake
+++ b/Modules/Compiler/GNU.cmake
@@ -45,11 +45,11 @@ macro(__compiler_gnu lang)
   endif()
 
   # Initial configuration flags.
-  set(CMAKE_${lang}_FLAGS_INIT "")
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-Os -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-O2 -g -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -Os -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O3 -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -O2 -g -DNDEBUG")
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
   set(CMAKE_${lang}_CREATE_ASSEMBLY_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")
   if(NOT APPLE OR NOT CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 4) # work around #4462
diff --git a/Modules/Compiler/Intel.cmake b/Modules/Compiler/Intel.cmake
index ff62804e52..8c3942cfe8 100644
--- a/Modules/Compiler/Intel.cmake
+++ b/Modules/Compiler/Intel.cmake
@@ -27,10 +27,10 @@ else()
   macro(__compiler_intel lang)
     set(CMAKE_${lang}_VERBOSE_FLAG "-v")
 
-    set(CMAKE_${lang}_FLAGS_INIT "")
-    set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g")
-    set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-Os")
-    set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O3")
-    set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
+    string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
+    string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g")
+    string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -Os")
+    string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O3")
+    string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -O2 -g")
   endmacro()
 endif()
diff --git a/Modules/Compiler/PGI-C.cmake b/Modules/Compiler/PGI-C.cmake
index da88c01164..85d6e7e0c2 100644
--- a/Modules/Compiler/PGI-C.cmake
+++ b/Modules/Compiler/PGI-C.cmake
@@ -1,4 +1,4 @@
 include(Compiler/PGI)
 __compiler_pgi(C)
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "${CMAKE_C_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
-set(CMAKE_C_FLAGS_RELEASE_INIT "${CMAKE_C_FLAGS_RELEASE_INIT} -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
diff --git a/Modules/Compiler/PGI-CXX.cmake b/Modules/Compiler/PGI-CXX.cmake
index 97c9555b10..896e29877e 100644
--- a/Modules/Compiler/PGI-CXX.cmake
+++ b/Modules/Compiler/PGI-CXX.cmake
@@ -1,4 +1,4 @@
 include(Compiler/PGI)
 __compiler_pgi(CXX)
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "${CMAKE_CXX_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "${CMAKE_CXX_FLAGS_RELEASE_INIT} -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -DNDEBUG")
diff --git a/Modules/Compiler/PGI-Fortran.cmake b/Modules/Compiler/PGI-Fortran.cmake
index 2866254feb..3765079a1f 100644
--- a/Modules/Compiler/PGI-Fortran.cmake
+++ b/Modules/Compiler/PGI-Fortran.cmake
@@ -4,7 +4,7 @@ __compiler_pgi(Fortran)
 set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-Mnofreeform")
 set(CMAKE_Fortran_FORMAT_FREE_FLAG "-Mfreeform")
 
-set(CMAKE_Fortran_FLAGS_INIT "${CMAKE_Fortran_FLAGS_INIT} -Mpreprocess -Kieee")
-set(CMAKE_Fortran_FLAGS_DEBUG_INIT "${CMAKE_Fortran_FLAGS_DEBUG_INIT} -Mbounds")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " -Mpreprocess -Kieee")
+string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " -Mbounds")
 
 set(CMAKE_Fortran_MODDIR_FLAG "-module ")
diff --git a/Modules/Compiler/PGI.cmake b/Modules/Compiler/PGI.cmake
index 797945f9a0..51069c2cfe 100644
--- a/Modules/Compiler/PGI.cmake
+++ b/Modules/Compiler/PGI.cmake
@@ -23,11 +23,11 @@ macro(__compiler_pgi lang)
   set(CMAKE_${lang}_VERBOSE_FLAG "-v")
 
   # Initial configuration flags.
-  set(CMAKE_${lang}_FLAGS_INIT "")
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g -O0")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-O2 -s")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-fast -O3 -Mipa=fast")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-O2 -gopt")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g -O0")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -O2 -s")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -fast -O3 -Mipa=fast")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -O2 -gopt")
 
   # Preprocessing and assembly rules.
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
diff --git a/Modules/Compiler/PathScale-C.cmake b/Modules/Compiler/PathScale-C.cmake
index 9db54afa06..94c7d08228 100644
--- a/Modules/Compiler/PathScale-C.cmake
+++ b/Modules/Compiler/PathScale-C.cmake
@@ -1,4 +1,4 @@
 include(Compiler/PathScale)
 __compiler_pathscale(C)
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "${CMAKE_C_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
-set(CMAKE_C_FLAGS_RELEASE_INIT "${CMAKE_C_FLAGS_RELEASE_INIT} -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
diff --git a/Modules/Compiler/PathScale-CXX.cmake b/Modules/Compiler/PathScale-CXX.cmake
index 4dd766048e..276b81ba51 100644
--- a/Modules/Compiler/PathScale-CXX.cmake
+++ b/Modules/Compiler/PathScale-CXX.cmake
@@ -1,4 +1,4 @@
 include(Compiler/PathScale)
 __compiler_pathscale(CXX)
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "${CMAKE_CXX_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "${CMAKE_CXX_FLAGS_RELEASE_INIT} -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -DNDEBUG")
diff --git a/Modules/Compiler/PathScale.cmake b/Modules/Compiler/PathScale.cmake
index 107f779a92..09ee2ba677 100644
--- a/Modules/Compiler/PathScale.cmake
+++ b/Modules/Compiler/PathScale.cmake
@@ -23,9 +23,9 @@ macro(__compiler_pathscale lang)
   set(CMAKE_${lang}_VERBOSE_FLAG "-v")
 
   # Initial configuration flags.
-  set(CMAKE_${lang}_FLAGS_INIT "")
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g -O0")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-Os")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O3")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-g -O2")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g -O0")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -Os")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O3")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -g -O2")
 endmacro()
diff --git a/Modules/Compiler/SunPro-ASM.cmake b/Modules/Compiler/SunPro-ASM.cmake
index 2fa8b99500..0d67400fea 100644
--- a/Modules/Compiler/SunPro-ASM.cmake
+++ b/Modules/Compiler/SunPro-ASM.cmake
@@ -8,11 +8,11 @@ set(CMAKE_SHARED_LIBRARY_RUNTIME_ASM_FLAG "-R")
 set(CMAKE_SHARED_LIBRARY_RUNTIME_ASM_FLAG_SEP ":")
 set(CMAKE_SHARED_LIBRARY_SONAME_ASM_FLAG "-h")
 
-set(CMAKE_ASM_FLAGS_INIT "")
-set(CMAKE_ASM_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_ASM_FLAGS_MINSIZEREL_INIT "-xO2 -xspace -DNDEBUG")
-set(CMAKE_ASM_FLAGS_RELEASE_INIT "-xO3 -DNDEBUG")
-set(CMAKE_ASM_FLAGS_RELWITHDEBINFO_INIT "-g -xO2 -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_INIT " ")
+string(APPEND CMAKE_ASM_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_ASM_FLAGS_MINSIZEREL_INIT " -xO2 -xspace -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_RELEASE_INIT " -xO3 -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_RELWITHDEBINFO_INIT " -g -xO2 -DNDEBUG")
 
 # Initialize ASM link type selection flags.  These flags are used when
 # building a shared library, shared module, or executable that links
diff --git a/Modules/Compiler/SunPro-C.cmake b/Modules/Compiler/SunPro-C.cmake
index c4529833d3..503684a36c 100644
--- a/Modules/Compiler/SunPro-C.cmake
+++ b/Modules/Compiler/SunPro-C.cmake
@@ -7,11 +7,11 @@ set(CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG "-R")
 set(CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG_SEP ":")
 set(CMAKE_SHARED_LIBRARY_SONAME_C_FLAG "-h")
 
-set(CMAKE_C_FLAGS_INIT "")
-set(CMAKE_C_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "-xO2 -xspace -DNDEBUG")
-set(CMAKE_C_FLAGS_RELEASE_INIT "-xO3 -DNDEBUG")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-g -xO2 -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_INIT " ")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -xO2 -xspace -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -xO3 -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -g -xO2 -DNDEBUG")
 
 # Initialize C link type selection flags.  These flags are used when
 # building a shared library, shared module, or executable that links
diff --git a/Modules/Compiler/SunPro-CXX.cmake b/Modules/Compiler/SunPro-CXX.cmake
index b4a5591b4c..ce01cddf0c 100644
--- a/Modules/Compiler/SunPro-CXX.cmake
+++ b/Modules/Compiler/SunPro-CXX.cmake
@@ -7,11 +7,11 @@ set(CMAKE_SHARED_LIBRARY_RUNTIME_CXX_FLAG "-R")
 set(CMAKE_SHARED_LIBRARY_RUNTIME_CXX_FLAG_SEP ":")
 set(CMAKE_SHARED_LIBRARY_SONAME_CXX_FLAG "-h")
 
-set(CMAKE_CXX_FLAGS_INIT "")
-set(CMAKE_CXX_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "-xO2 -xspace -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "-xO3 -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-g -xO2 -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_INIT " ")
+string(APPEND CMAKE_CXX_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -xO2 -xspace -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -xO3 -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT " -g -xO2 -DNDEBUG")
 
 # Initialize C link type selection flags.  These flags are used when
 # building a shared library, shared module, or executable that links
diff --git a/Modules/Compiler/SunPro-Fortran.cmake b/Modules/Compiler/SunPro-Fortran.cmake
index 610e19176a..a0e07d4cb8 100644
--- a/Modules/Compiler/SunPro-Fortran.cmake
+++ b/Modules/Compiler/SunPro-Fortran.cmake
@@ -10,11 +10,11 @@ set(CMAKE_SHARED_LIBRARY_RUNTIME_Fortran_FLAG_SEP ":")
 set(CMAKE_SHARED_LIBRARY_SONAME_Fortran_FLAG "-h")
 set(CMAKE_EXECUTABLE_RUNTIME_Fortran_FLAG "-R")
 
-set(CMAKE_Fortran_FLAGS_INIT "")
-set(CMAKE_Fortran_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "-xO2 -xspace -DNDEBUG")
-set(CMAKE_Fortran_FLAGS_RELEASE_INIT "-xO3 -DNDEBUG")
-set(CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT "-g -xO2 -DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " ")
+string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_Fortran_FLAGS_MINSIZEREL_INIT " -xO2 -xspace -DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " -xO3 -DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT " -g -xO2 -DNDEBUG")
 set(CMAKE_Fortran_MODDIR_FLAG "-moddir=")
 set(CMAKE_Fortran_MODPATH_FLAG "-M")
 
diff --git a/Modules/Compiler/TinyCC-C.cmake b/Modules/Compiler/TinyCC-C.cmake
index f7937acdf5..fbd2841e33 100644
--- a/Modules/Compiler/TinyCC-C.cmake
+++ b/Modules/Compiler/TinyCC-C.cmake
@@ -1,8 +1,8 @@
 set(CMAKE_SHARED_LIBRARY_CREATE_C_FLAGS "-shared")
 
 # no optimization in tcc:
-set (CMAKE_C_FLAGS_INIT "")
-set (CMAKE_C_FLAGS_DEBUG_INIT "-g")
-set (CMAKE_C_FLAGS_MINSIZEREL_INIT "-DNDEBUG")
-set (CMAKE_C_FLAGS_RELEASE_INIT "-DNDEBUG")
-set (CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-g -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_INIT " ")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -g -DNDEBUG")
diff --git a/Modules/Compiler/XL-ASM.cmake b/Modules/Compiler/XL-ASM.cmake
index 212179e34e..9177b392bb 100644
--- a/Modules/Compiler/XL-ASM.cmake
+++ b/Modules/Compiler/XL-ASM.cmake
@@ -2,11 +2,11 @@ set(CMAKE_ASM_VERBOSE_FLAG "-V")
 
 # -qthreaded     = Ensures that all optimizations will be thread-safe
 # -qhalt=e       = Halt on error messages (rather than just severe errors)
-set(CMAKE_ASM_FLAGS_INIT "-qthreaded -qhalt=e -qsourcetype=assembler")
+string(APPEND CMAKE_ASM_FLAGS_INIT " -qthreaded -qhalt=e -qsourcetype=assembler")
 
-set(CMAKE_ASM_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_ASM_FLAGS_RELEASE_INIT "-O -DNDEBUG")
-set(CMAKE_ASM_FLAGS_MINSIZEREL_INIT "-O -DNDEBUG")
-set(CMAKE_ASM_FLAGS_RELWITHDEBINFO_INIT "-g -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_ASM_FLAGS_RELEASE_INIT " -O -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_MINSIZEREL_INIT " -O -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_RELWITHDEBINFO_INIT " -g -DNDEBUG")
 
 set(CMAKE_ASM_SOURCE_FILE_EXTENSIONS s )
diff --git a/Modules/Compiler/XL-C.cmake b/Modules/Compiler/XL-C.cmake
index 97dd017891..f976c9912c 100644
--- a/Modules/Compiler/XL-C.cmake
+++ b/Modules/Compiler/XL-C.cmake
@@ -1,8 +1,8 @@
 include(Compiler/XL)
 __compiler_xl(C)
-set(CMAKE_C_FLAGS_RELEASE_INIT "${CMAKE_C_FLAGS_RELEASE_INIT} -DNDEBUG")
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "${CMAKE_C_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
 
 # -qthreaded     = Ensures that all optimizations will be thread-safe
 # -qhalt=e       = Halt on error messages (rather than just severe errors)
-set(CMAKE_C_FLAGS_INIT "-qthreaded -qhalt=e")
+string(APPEND CMAKE_C_FLAGS_INIT " -qthreaded -qhalt=e")
diff --git a/Modules/Compiler/XL-CXX.cmake b/Modules/Compiler/XL-CXX.cmake
index 41372c15ba..545d657329 100644
--- a/Modules/Compiler/XL-CXX.cmake
+++ b/Modules/Compiler/XL-CXX.cmake
@@ -1,11 +1,11 @@
 include(Compiler/XL)
 __compiler_xl(CXX)
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "${CMAKE_CXX_FLAGS_RELEASE_INIT} -DNDEBUG")
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "${CMAKE_CXX_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
 
 # -qthreaded     = Ensures that all optimizations will be thread-safe
 # -qhalt=e       = Halt on error messages (rather than just severe errors)
-set(CMAKE_CXX_FLAGS_INIT "-qthreaded -qhalt=e")
+string(APPEND CMAKE_CXX_FLAGS_INIT " -qthreaded -qhalt=e")
 
 set(CMAKE_CXX_COMPILE_OBJECT
   "<CMAKE_CXX_COMPILER> -+ <DEFINES> <INCLUDES> <FLAGS> -o <OBJECT> -c <SOURCE>")
diff --git a/Modules/Compiler/XL-Fortran.cmake b/Modules/Compiler/XL-Fortran.cmake
index ae9df4e4b7..6bab6f69e0 100644
--- a/Modules/Compiler/XL-Fortran.cmake
+++ b/Modules/Compiler/XL-Fortran.cmake
@@ -10,7 +10,7 @@ set(CMAKE_Fortran_DEFINE_FLAG "-WF,-D")
 
 # -qthreaded     = Ensures that all optimizations will be thread-safe
 # -qhalt=e       = Halt on error messages (rather than just severe errors)
-set(CMAKE_Fortran_FLAGS_INIT "-qthreaded -qhalt=e")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " -qthreaded -qhalt=e")
 
 # xlf: 1501-214 (W) command option E reserved for future use - ignored
 set(CMAKE_Fortran_CREATE_PREPROCESSED_SOURCE)
diff --git a/Modules/Compiler/XL.cmake b/Modules/Compiler/XL.cmake
index bf4f5541c6..1f2b1455e3 100644
--- a/Modules/Compiler/XL.cmake
+++ b/Modules/Compiler/XL.cmake
@@ -29,10 +29,10 @@ macro(__compiler_xl lang)
   set(CMAKE_${lang}_VERBOSE_FLAG "-V")
   set(CMAKE_${lang}_COMPILE_OPTIONS_PIC "-qpic")
 
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-O")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-g")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -O")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -g")
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
   set(CMAKE_${lang}_CREATE_ASSEMBLY_SOURCE     "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")
 
diff --git a/Modules/Platform/ARTOS-GNU-C.cmake b/Modules/Platform/ARTOS-GNU-C.cmake
index 967d0e7c06..fe8d782e3d 100644
--- a/Modules/Platform/ARTOS-GNU-C.cmake
+++ b/Modules/Platform/ARTOS-GNU-C.cmake
@@ -1,9 +1,9 @@
 # Define ARTOS to select proper behaviour and tell preprocessor to accept C++ style comments.
-set(CMAKE_C_FLAGS_INIT "-DARTOS -Xp -+")
+string(APPEND CMAKE_C_FLAGS_INIT " -DARTOS -Xp -+")
 # ac doesn't support -g properly and doesn't support the normal gcc optimization options. Just use the defaults set by ac.
-set(CMAKE_C_FLAGS_DEBUG_INIT "")
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "-DNDEBUG")
-set(CMAKE_C_FLAGS_RELEASE_INIT "-DNDEBUG")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " ")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -DNDEBUG")
 # Most projects expect the stdio functions to be available.
 set(CMAKE_C_STANDARD_LIBRARIES_INIT "stdio.a")
diff --git a/Modules/Platform/Generic-ADSP-C.cmake b/Modules/Platform/Generic-ADSP-C.cmake
index 4b9ed9d073..de1cee2988 100644
--- a/Modules/Platform/Generic-ADSP-C.cmake
+++ b/Modules/Platform/Generic-ADSP-C.cmake
@@ -4,10 +4,10 @@ include(Platform/Generic-ADSP-Common)
 
 set(CMAKE_C_OUTPUT_EXTENSION ".doj")
 
-set(CMAKE_C_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "")
-set(CMAKE_C_FLAGS_RELEASE_INIT "")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "")
+string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " ")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " ")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " ")
 
 set(CMAKE_C_CREATE_STATIC_LIBRARY
     "<CMAKE_C_COMPILER> -build-lib -proc ${ADSP_PROCESSOR} -si-revision ${ADSP_PROCESSOR_SILICIUM_REVISION} -o <TARGET> <CMAKE_C_LINK_FLAGS> <OBJECTS>")
diff --git a/Modules/Platform/Generic-ADSP-CXX.cmake b/Modules/Platform/Generic-ADSP-CXX.cmake
index 9673aef408..0cde8f2e60 100644
--- a/Modules/Platform/Generic-ADSP-CXX.cmake
+++ b/Modules/Platform/Generic-ADSP-CXX.cmake
@@ -2,10 +2,10 @@ include(Platform/Generic-ADSP-Common)
 
 set(CMAKE_CXX_OUTPUT_EXTENSION ".doj")
 
-set(CMAKE_CXX_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "")
+string(APPEND CMAKE_CXX_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " ")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " ")
+string(APPEND CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT " ")
 
 set(CMAKE_CXX_CREATE_STATIC_LIBRARY
      "<CMAKE_CXX_COMPILER> -build-lib -proc ${ADSP_PROCESSOR} -si-revision ${ADSP_PROCESSOR_SILICIUM_REVISION} -o <TARGET> <CMAKE_CXX_LINK_FLAGS> <OBJECTS>")
diff --git a/Modules/Platform/Generic-SDCC-C.cmake b/Modules/Platform/Generic-SDCC-C.cmake
index a1ca81243e..bbefe193ed 100644
--- a/Modules/Platform/Generic-SDCC-C.cmake
+++ b/Modules/Platform/Generic-SDCC-C.cmake
@@ -30,7 +30,7 @@ set(CMAKE_AR "${SDCCLIB_EXECUTABLE}" CACHE FILEPATH "The sdcc librarian" FORCE)
 
 # CMAKE_C_FLAGS_INIT and CMAKE_EXE_LINKER_FLAGS_INIT should be set in a CMAKE_SYSTEM_PROCESSOR file
 if(NOT DEFINED CMAKE_C_FLAGS_INIT)
-  set(CMAKE_C_FLAGS_INIT "-mmcs51 --model-small")
+  string(APPEND CMAKE_C_FLAGS_INIT " -mmcs51 --model-small")
 endif()
 
 if(NOT DEFINED CMAKE_EXE_LINKER_FLAGS_INIT)
diff --git a/Modules/Platform/HP-UX-HP-CXX.cmake b/Modules/Platform/HP-UX-HP-CXX.cmake
index 6d90191cb7..d37d2b055d 100644
--- a/Modules/Platform/HP-UX-HP-CXX.cmake
+++ b/Modules/Platform/HP-UX-HP-CXX.cmake
@@ -8,7 +8,7 @@ set(CMAKE_CXX_CREATE_ASSEMBLY_SOURCE
   "rm -f `basename \"<SOURCE>\" | sed 's/\\.[^./]*$$//'`.o"
   )
 
-set(CMAKE_CXX_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "+O3 -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "+O2 -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-g")
+string(APPEND CMAKE_CXX_FLAGS_DEBUG_INIT " -g")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " +O3 -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " +O2 -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT " -g")
diff --git a/Modules/Platform/HP-UX-HP.cmake b/Modules/Platform/HP-UX-HP.cmake
index 3935c31c1f..398d6fba97 100644
--- a/Modules/Platform/HP-UX-HP.cmake
+++ b/Modules/Platform/HP-UX-HP.cmake
@@ -27,7 +27,7 @@ macro(__hpux_compiler_hp lang)
   set(CMAKE_SHARED_LIBRARY_RUNTIME_${lang}_FLAG_SEP ":")
   set(CMAKE_SHARED_LIBRARY_SONAME_${lang}_FLAG "-Wl,+h")
 
-  set(CMAKE_${lang}_FLAGS_INIT "")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ")
 
   set(CMAKE_${lang}_LINK_FLAGS "-Wl,+s,+nodefaultrpath")
 endmacro()
diff --git a/Modules/Platform/Windows-Embarcadero.cmake b/Modules/Platform/Windows-Embarcadero.cmake
index 102e3a6510..8a87db3712 100644
--- a/Modules/Platform/Windows-Embarcadero.cmake
+++ b/Modules/Platform/Windows-Embarcadero.cmake
@@ -132,10 +132,10 @@ macro(__embarcadero_language lang)
     )
 
   # Initial configuration flags.
-  set(CMAKE_${lang}_FLAGS_INIT "${_tM}")
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-Od -v")
-  set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-O1 -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O2 -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-Od")
+  string(APPEND CMAKE_${lang}_FLAGS_INIT " ${_tM}")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -Od -v")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -O1 -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O2 -DNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -Od")
   set(CMAKE_${lang}_STANDARD_LIBRARIES_INIT "import32.lib")
 endmacro()
diff --git a/Modules/Platform/Windows-Intel-Fortran.cmake b/Modules/Platform/Windows-Intel-Fortran.cmake
index 1b93db85f1..3981a092b3 100644
--- a/Modules/Platform/Windows-Intel-Fortran.cmake
+++ b/Modules/Platform/Windows-Intel-Fortran.cmake
@@ -4,8 +4,8 @@ set(_COMPILE_Fortran " /fpp")
 set(CMAKE_Fortran_MODDIR_FLAG "-module:")
 set(CMAKE_Fortran_STANDARD_LIBRARIES_INIT "user32.lib")
 __windows_compiler_intel(Fortran)
-set (CMAKE_Fortran_FLAGS_INIT "/W1 /nologo /fpp /libs:dll /threads")
-set (CMAKE_Fortran_FLAGS_DEBUG_INIT "/Od /debug:full /dbglibs")
-set (CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "/O1 /DNDEBUG")
-set (CMAKE_Fortran_FLAGS_RELEASE_INIT "/O2 /DNDEBUG")
-set (CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT "/O2 /debug:full /DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_INIT " /W1 /nologo /fpp /libs:dll /threads")
+string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " /Od /debug:full /dbglibs")
+string(APPEND CMAKE_Fortran_FLAGS_MINSIZEREL_INIT " /O1 /DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " /O2 /DNDEBUG")
+string(APPEND CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT " /O2 /debug:full /DNDEBUG")
diff --git a/Modules/Platform/Windows-MSVC.cmake b/Modules/Platform/Windows-MSVC.cmake
index 3fd68024e7..b1969a2e40 100644
--- a/Modules/Platform/Windows-MSVC.cmake
+++ b/Modules/Platform/Windows-MSVC.cmake
@@ -303,17 +303,17 @@ macro(__windows_compiler_msvc lang)
     if(CMAKE_VS_PLATFORM_TOOLSET MATCHES "v[0-9]+_clang_.*")
       # note: MSVC 14 2015 Update 1 sets -fno-ms-compatibility by default, but this does not allow one to compile many projects
       # that include MS's own headers. CMake itself is affected project too.
-      set(CMAKE_${lang}_FLAGS_INIT "${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} -fms-extensions -fms-compatibility -D_WINDOWS -Wall${_FLAGS_${lang}}")
-      set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-D_DEBUG /MDd -gline-tables-only -fno-inline -O0 ${_RTC1}")
-      set(CMAKE_${lang}_FLAGS_RELEASE_INIT "/MD -O2 -DNDEBUG")
-      set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "/MD -gline-tables-only -O2 -fno-inline -DNDEBUG")
-      set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "/MD -DNDEBUG") # TODO: Add '-Os' once VS generator maps it properly for Clang
+      string(APPEND CMAKE_${lang}_FLAGS_INIT " ${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} -fms-extensions -fms-compatibility -D_WINDOWS -Wall${_FLAGS_${lang}}")
+      string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -D_DEBUG /MDd -gline-tables-only -fno-inline -O0 ${_RTC1}")
+      string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " /MD -O2 -DNDEBUG")
+      string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " /MD -gline-tables-only -O2 -fno-inline -DNDEBUG")
+      string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " /MD -DNDEBUG") # TODO: Add '-Os' once VS generator maps it properly for Clang
     else()
-      set(CMAKE_${lang}_FLAGS_INIT "${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} /D_WINDOWS /W3${_FLAGS_${lang}}")
-      set(CMAKE_${lang}_FLAGS_DEBUG_INIT "/D_DEBUG /MDd /Zi /Ob0 /Od ${_RTC1}")
-      set(CMAKE_${lang}_FLAGS_RELEASE_INIT "/MD /O2 /Ob2 /DNDEBUG")
-      set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "/MD /Zi /O2 /Ob1 /DNDEBUG")
-      set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "/MD /O1 /Ob1 /DNDEBUG")
+      string(APPEND CMAKE_${lang}_FLAGS_INIT " ${_PLATFORM_DEFINES}${_PLATFORM_DEFINES_${lang}} /D_WINDOWS /W3${_FLAGS_${lang}}")
+      string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " /D_DEBUG /MDd /Zi /Ob0 /Od ${_RTC1}")
+      string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " /MD /O2 /Ob2 /DNDEBUG")
+      string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " /MD /Zi /O2 /Ob1 /DNDEBUG")
+      string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " /MD /O1 /Ob1 /DNDEBUG")
     endif()
   endif()
   set(CMAKE_${lang}_LINKER_SUPPORTS_PDB ON)
@@ -323,7 +323,7 @@ macro(__windows_compiler_msvc lang)
     set(CMAKE_RC_COMPILER_INIT rc)
   endif()
   if(NOT CMAKE_RC_FLAGS_INIT)
-    set(CMAKE_RC_FLAGS_INIT "${_PLATFORM_DEFINES} ${_PLATFORM_DEFINES_${lang}}")
+    string(APPEND CMAKE_RC_FLAGS_INIT " ${_PLATFORM_DEFINES} ${_PLATFORM_DEFINES_${lang}}")
   endif()
 
   enable_language(RC)
diff --git a/Modules/Platform/Windows-OpenWatcom.cmake b/Modules/Platform/Windows-OpenWatcom.cmake
index 7147600ebf..269f9230b4 100644
--- a/Modules/Platform/Windows-OpenWatcom.cmake
+++ b/Modules/Platform/Windows-OpenWatcom.cmake
@@ -52,13 +52,13 @@ set(CMAKE_BUILD_TYPE_INIT Debug)
 # single/multi-threaded                 /-bm
 # static/DLL run-time libraries         /-br
 # default is setup for multi-threaded + DLL run-time libraries
-set (CMAKE_C_FLAGS_INIT "-bt=nt -w3 -dWIN32 -br -bm")
-set (CMAKE_CXX_FLAGS_INIT "-bt=nt -xs -w3 -dWIN32 -br -bm")
+string(APPEND CMAKE_C_FLAGS_INIT " -bt=nt -w3 -dWIN32 -br -bm")
+string(APPEND CMAKE_CXX_FLAGS_INIT " -bt=nt -xs -w3 -dWIN32 -br -bm")
 foreach(lang C CXX)
-  set (CMAKE_${lang}_FLAGS_DEBUG_INIT "-d2")
-  set (CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-s -os -d0 -dNDEBUG")
-  set (CMAKE_${lang}_FLAGS_RELEASE_INIT "-s -ot -d0 -dNDEBUG")
-  set (CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-s -ot -d1 -dNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -d2")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -s -os -d0 -dNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -s -ot -d0 -dNDEBUG")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -s -ot -d1 -dNDEBUG")
 endforeach()
 
 foreach(type CREATE_SHARED_LIBRARY CREATE_SHARED_MODULE LINK_EXECUTABLE)