fix macos building with sdl

Author: Sulfrix

CMakeLists.txt

@@ -9,6 +9,10 @@ if (POLICY CMP0141)
   set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT "$<IF:$<AND:$<C_COMPILER_ID:MSVC>,$<CXX_COMPILER_ID:MSVC>>,$<$<CONFIG:Debug,RelWithDebInfo>:EditAndContinue>,$<$<CONFIG:Debug,RelWithDebInfo>:ProgramDatabase>>")
 endif()
 
+if(APPLE)
+  enable_language(OBJC)
+endif()
+
 project ("Encore" LANGUAGES C CXX)
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall")
 # Include sub-projects.