correct mac compilation

SDL now leverages https://cmake.org/cmake/help/v3.10/command/enable_language.html

Tools/CMake/basics.cmake

@@ -467,6 +467,19 @@ if(WIN32)
         ENDFOREACH()
     endif()
 else()
+    if(${CMAKE_VERSION} VERSION_LESS "3.16.0")
+        macro(CHECK_OBJC_SOURCE_COMPILES SOURCE VAR)
+            set(PREV_REQUIRED_DEFS "${CMAKE_REQUIRED_DEFINITIONS}")
+            set(CMAKE_REQUIRED_DEFINITIONS "-x objective-c ${PREV_REQUIRED_DEFS}")
+            CHECK_C_SOURCE_COMPILES(${SOURCE} ${VAR})
+            set(CMAKE_REQUIRED_DEFINITIONS "${PREV_REQUIRED_DEFS}")
+        endmacro()
+    else()
+        include(CheckOBJCSourceCompiles)
+        if (APPLE)
+            enable_language(OBJC)
+        endif()
+    endif()
     # TODO: improve default settings on other platforms
     set(TORQUE_CXX_FLAGS_EXECUTABLES "" CACHE STRING "")
     mark_as_advanced(TORQUE_CXX_FLAGS_EXECUTABLES)