GtkDoc.cmake - include LDFLAGS in gtkdoc-scangobj command line

When a library provides no way to find linker flags for linking with it,
the build system usually depends on the user to necessary put -L flags
in LDFLAGS environment variable in order to find it. However, GtkDoc
module constructs the command line by itself, and it forgets to add
LDFLAGS to the command line of gtkdoc-scangobj.

It is especially important to include LDFLAGS on non-GNU systems. For
example, FreeBSD libc doesn't include a gettext implementation. GLib
requires gettext, and it pulls in an external gettext runtime for it.
However, gettext-runtime doesn't include a .pc file, so LDFLAGS is
required if gettext-runtime isn't installed in the same prefix as GLib.
Failing to include LDFLAGS in --ldflags passed to gtkdoc-scangobj can
result in a linking error because -lintl cannot be found.

In addition to the change to include LDFLAGS, this commit also changes
the following things:

 - Instead of constructing _scangobj_ldflags in reverse order, do it in
   normal order. Appending is easier to understand than prepending, and
   the linker also interprets -L and -l flags in normal order.

 - Move -L${LIB_INSTALL_DIR} to the bottom. This is what the comment
   says, and it is expected to work because we no longer constructs
   _scangobj_ldflags in reverse order.

 - Move NOT TARGET case to a separate loop. This change is pulled from
   evolution-data-server. The reason of doing so is that we should put
   internal libraries in front of external libraries, so the linker
   always prefers libraries built as parts of the project to libraries
   installed on the system.

1 files changed, 14 insertions, 5 deletions

diff --git a/cmake/modules/GtkDoc.cmake b/cmake/modules/GtkDoc.cmake
index 03a0c1dd..cc5b2bb4 100644
--- a/cmake/modules/GtkDoc.cmake
+++ b/cmake/modules/GtkDoc.cmake
@@ -94,9 +94,8 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
     list(APPEND _scangobj_deps ${opt})
   endforeach()
 
-  # Add them as the last, thus in-tree headers/libs have precedence
+  # Add it as the last, thus in-tree headers have precedence
   list(APPEND _scangobj_cflags_list -I${INCLUDE_INSTALL_DIR})
-  list(APPEND _scangobj_ldflags -L${LIB_INSTALL_DIR})
 
   if(_scangobj_deps)
     list(REMOVE_DUPLICATES _scangobj_deps)
@@ -119,7 +118,7 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
         if(NOT _output_name)
           set(_output_name ${opt})
         endif()
-        set(_scangobj_ldflags "-L$<TARGET_FILE_DIR:${opt}> -l${_output_name} ${_scangobj_ldflags}")
+        set(_scangobj_ldflags "${_scangobj_ldflags} -L$<TARGET_FILE_DIR:${opt}> -l${_output_name}")
 
         if(_target_type STREQUAL "SHARED_LIBRARY" OR (_target_type STREQUAL "MODULE_LIBRARY"))
           set(_scangobj_ld_lib_dirs "${_scangobj_ld_lib_dirs}:$<TARGET_FILE_DIR:${opt}>")
@@ -127,11 +126,21 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
         unset(_output_name)
       endif()
       unset(_target_type)
-    else()
-      set(_scangobj_ldflags "${opt} ${_scangobj_ldflags}")
     endif()
   endforeach()
 
+  # Add extra flags from LDFLAGS environment variable
+  set(_scangobj_ldflags "${_scangobj_ldflags} ${CMAKE_SHARED_LINKER_FLAGS}")
+
+  foreach(opt IN LISTS _scangobj_deps)
+    if(NOT TARGET ${opt})
+      set(_scangobj_ldflags "${_scangobj_ldflags} ${opt}")
+    endif()
+  endforeach()
+
+  # Add it as the last, thus in-tree libs have precedence
+  set(_scangobj_ldflags "${_scangobj_ldflags} -L${LIB_INSTALL_DIR}")
+
   set(_scangobj_prefix ${CMAKE_COMMAND} -E env LD_LIBRARY_PATH="${_scangobj_ld_lib_dirs}:${LIB_INSTALL_DIR}:$ENV{LD_LIBRARY_PATH}")
 
 #  if(NOT (_scangobj_cflags STREQUAL ""))