If CG isn't available, still compile and fallback on GLSL

Source/Plugins/Plugin_VideoOGL/CMakeLists.txt

@@ -23,7 +23,7 @@ if(wxWidgets_FOUND)
 	set(LIBS	${LIBS} ${wxWidgets_LIBRARIES})
 endif(wxWidgets_FOUND)
 
-if(WIN32 OR ${CMAKE_SYSTEM_NAME} MATCHES "Linux")
+if(HAVE_CG AND (APPLE OR WIN32 OR ${CMAKE_SYSTEM_NAME} MATCHES "Linux"))
 	set(LIBS	${LIBS} Cg CgGL)
 elseif(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
 	list(APPEND LIBS "${CMAKE_SOURCE_DIR}/Externals/Cg/Cg.framework")