CMake: always define BROTLI_LIBRARIES

Previously FREETYPE_LIBRARIES would sometimes contain
BROTLI libraries, since some configurations set them separately,
declare them separately under all configurations to avoid
changes to one platform breaking others.

Also quiets uninitialized variable warning.

build_files/cmake/platform/platform_apple.cmake

@@ -145,9 +145,10 @@ endif()
 
 # FreeType compiled with Brotli compression for woff2.
 find_package(Freetype REQUIRED)
-list(APPEND FREETYPE_LIBRARIES
+set(BROTLI_LIBRARIES
   ${LIBDIR}/brotli/lib/libbrotlicommon-static.a
-  ${LIBDIR}/brotli/lib/libbrotlidec-static.a)
+  ${LIBDIR}/brotli/lib/libbrotlidec-static.a
+)
 
 if(WITH_IMAGE_OPENEXR)
   find_package(OpenEXR)

build_files/cmake/platform/platform_unix.cmake

@@ -144,6 +144,9 @@ if(NOT WITH_SYSTEM_FREETYPE)
     # list(APPEND FREETYPE_LIBRARIES
     #   ${BROTLI_LIBRARIES}
     # )
+  else()
+    # Quiet warning as this variable will be used after `FREETYPE_LIBRARIES`.
+    set(BROTLI_LIBRARIES "")
   endif()
   check_freetype_for_brotli()
 endif()
@@ -604,6 +607,8 @@ if(WITH_SYSTEM_FREETYPE)
     message(FATAL_ERROR "Failed finding system FreeType version!")
   endif()
   check_freetype_for_brotli()
+  # Quiet warning as this variable will be used after `FREETYPE_LIBRARIES`.
+  set(BROTLI_LIBRARIES "")
 endif()
 
 if(WITH_LZO AND WITH_SYSTEM_LZO)

build_files/cmake/platform/platform_win32.cmake

@@ -364,9 +364,12 @@ set(FREETYPE_INCLUDE_DIRS
 )
 set(FREETYPE_LIBRARIES
   ${LIBDIR}/freetype/lib/freetype2ST.lib
+)
+set(BROTLI_LIBRARIES
   ${LIBDIR}/brotli/lib/brotlidec-static.lib
   ${LIBDIR}/brotli/lib/brotlicommon-static.lib
 )
+
 windows_find_package(Freetype REQUIRED)
 
 if(WITH_FFTW3)