Fixed bug 3882 - cmake fix for osx

Ozkan Sezer

In my cross-build environment with cmake-2.8.12.1, cmake does not add
SDL_coreaudio.m to its makefiles and the result is a failure. The fix
is simple: set the language to C for it as it is done at other places
in CMakeLists.txt.

CMakeLists.txt

@@ -1352,7 +1352,7 @@ elseif(APPLE)
   # !!! FIXME: we need Carbon for some very old API calls in
   # !!! FIXME:  src/video/cocoa/SDL_cocoakeyboard.c, but we should figure out
   # !!! FIXME:  how to dump those.
-  if (APPLE AND NOT IOS)
+  if(NOT IOS)
     set(SDL_FRAMEWORK_COCOA 1)
     set(SDL_FRAMEWORK_CARBON 1)
   endif()
@@ -1373,6 +1373,8 @@ elseif(APPLE)
   if(SDL_AUDIO)
     set(SDL_AUDIO_DRIVER_COREAUDIO 1)
     file(GLOB AUDIO_SOURCES ${SDL2_SOURCE_DIR}/src/audio/coreaudio/*.m)
+    # !!! FIXME: modern CMake doesn't need "LANGUAGE C" for Objective-C.
+    set_source_files_properties(${AUDIO_SOURCES} PROPERTIES LANGUAGE C)
     set(SOURCE_FILES ${SOURCE_FILES} ${AUDIO_SOURCES})
     set(HAVE_SDL_AUDIO TRUE)
     set(SDL_FRAMEWORK_COREAUDIO 1)