Fix CMake build to be compatible with FetchContent

Recent versions of CMake have improved support for including
dependencies, using the FetchContent module, which allows a dependency
to be imported as a subproject and then later found automatically by
calls to `find_package`.

This change makes libtiff's CMake better behaved when used as a
sub-project:

- CMake has a single global namespace for all target names in all
  sub-projects.  This commit renames the following CMake targets:

  - port -> tiff_port
  - mkg3states -> tiff_mkg3states
  - faxtable -> tiff_faxtable
  - release -> tiff_release

- When building TIFF as a sub-project, it is not normally useful to
  create install rules for its targets.  This commit adds a
  `tiff-install` option that controls whether the install rules are
  added and defaults to OFF when libtiff is included as a sub-project.

- Previously, libtiff set `BUILD_SHARED_LIBS` to ON by default.  With
  this commit, that default is only set if libtiff is the top-level
  project.

- When using `find_package(TIFF)`, the targets `TIFF::TIFF` and
  `TIFF::CXX` are defined.  This commit makes libtiff itself define
  those targets as aliases, to allow other cmake projects to use
  either `find_package` or `FetchContent` interchangeably.

- Adds ZSTD_HAVE_DECOMPRESS_STREAM variable which may be set to bypass
  `check_symbol_exists` call.  Fixes
  https://gitlab.com/libtiff/libtiff/-/issues/472.

1 files changed, 5 insertions, 5 deletions

diff --git a/port/CMakeLists.txt b/port/CMakeLists.txt
index fd459162..04bd3ea8 100755
--- a/port/CMakeLists.txt
+++ b/port/CMakeLists.txt
@@ -31,21 +31,21 @@ set(port_HEADERS libport.h)
 
 # Only build if any needed features are missing
 if(NOT HAVE_GETOPT)
-  add_library(port STATIC ../placeholder.h)
+  add_library(tiff_port STATIC ../placeholder.h)
 
   # Add getopt if missing
   if(NOT HAVE_GETOPT)
-    target_sources(port PUBLIC
+    target_sources(tiff_port PUBLIC
             ${CMAKE_CURRENT_SOURCE_DIR}/getopt.c)
   endif()
 
-  target_include_directories(port PUBLIC
+  target_include_directories(tiff_port PUBLIC
           ${CMAKE_CURRENT_BINARY_DIR}
           ${CMAKE_CURRENT_SOURCE_DIR})
 else()
   # Dummy interface library
-  add_library(port INTERFACE)
-  target_include_directories(port INTERFACE
+  add_library(tiff_port INTERFACE)
+  target_include_directories(tiff_port INTERFACE
           ${CMAKE_CURRENT_BINARY_DIR}
           ${CMAKE_CURRENT_SOURCE_DIR})
 endif()