Update RapidJSON handling in CMakeLists.txt

Set LIBCZI_BUILD_PREFER_EXTERNALPACKAGE_RAPIDJSON to OFF to ensure automatic download and build of RapidJSON. Added comments to clarify RapidJSON as a header-only library and noted issues with version 1.1.0 on GCC 14.2 with msys2. Using a later version from the master branch (commit 7c73dd7de7c4f14379b781418c6e947ad464c818).

CMakeLists.txt

@@ -75,7 +75,11 @@ check_cxx_symbol_exists(pwrite unistd.h HAVE_UNISTD_H_PWRITE)
 BoolToFoundNotFound(HAVE_UNISTD_H_PWRITE HAVE_UNISTD_H_PWRITE_TEXT)
 message("check for open -> ${HAVE_FCNTL_H_OPEN_TEXT} ; check for pread -> ${HAVE_UNISTD_H_PREAD_TEXT} ; check for pwrite -> ${HAVE_UNISTD_H_PWRITE_TEXT}")
 
-# determine whether the Win32-API can be used (in other words: whether we are on a Windows-platform or targetting the Windows-platform)
+# Determine whether the Win32-API can be used (in other words: whether we are on a Windows-platform or targetting the Windows-platform).
+# Note that just checking for WIN32 is not sufficient here, as this is not defined with environments such as msys2. In those cases, UNIX is defined.
+# The meaning of this switch is: whether Win32-API can be used (and this affects not only compilation but e.g. also linking to the Win32-API, as
+# it is not automatically linked to when using MinGW or Cygwin).
+# TODO(JBL): check how we can make cross-compiling to Windows work
 if (WIN32 OR CYGWIN OR MSYS OR MINGW)
   set(LIBCZI_HAVE_WIN32_API ON)
 else()

Src/CZICmd/CMakeLists.txt

@@ -39,8 +39,10 @@ if (LIBCZI_BUILD_PREFER_EXTERNALPACKAGE_RAPIDJSON)
         ]=])
     endif()
 else()
-    # since "RapidJSON" is a header-only library, we just have to download it and point to the include directory
-     FetchContent_Declare(
+    # Since "RapidJSON" is a header-only library, we just have to download it and point to the include directory.
+    # Note: when using v1.1.0 of RapidJSON (the latest release) there we problems (with GCC14.2 with msys2), so
+    #        we use a later version from the master branch.
+    FetchContent_Declare(
             RapidJSON
             GIT_REPOSITORY https://github.com/Tencent/rapidjson.git
             GIT_TAG        7c73dd7de7c4f14379b781418c6e947ad464c818 # master as of 2024-08-16