Update CMakeLists.txt

revert CoreAudio to default for mac build

Engine/lib/CMakeLists.txt

@@ -199,7 +199,7 @@ if(TORQUE_SFX_OPENAL)
     advanced_option(TORQUE_OGGVORBIS "Enable OGG Vorbis" ON)
     advanced_option(ALSOFT_EAX "Enable legacy EAX extensions" ${WIN32})
     advanced_option(ALSOFT_UPDATE_BUILD_VERSION "Update git build version info" ON)
-    advanced_option(ALSOFT_BACKEND_COREAUDIO "Enable CoreAudio backend" ON)
+    mark_as_advanced(ALSOFT_BACKEND_COREAUDIO)
     advanced_option(ALSOFT_BACKEND_DSOUND "Enable DirectSound backend" OFF)    
     advanced_option(ALSOFT_BACKEND_JACK "Enable Jack backend" OFF)
     advanced_option(ALSOFT_BACKEND_OBOE "Enable OBOE backend" OFF)