SDL: cmake: fix Metal detection

SDL Commits
1 
From 71e06a536a6fb9eebf15881e9a1ddaf2f463a5f1 Mon Sep 17 00:00:00 2001
From: Eric Wasylishen <[EMAIL REDACTED]>
Date: Fri, 26 Nov 2021 18:27:34 -0700
Subject: [PATCH] cmake: fix Metal detection

Confirmed to work on:
macOS 10.15.7
XCode Version 12.4 (12D4e)
---
 CMakeLists.txt | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5f19e445cb8..4ea56547451 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1992,9 +1992,7 @@ elseif(APPLE)
     endif()
 
     if(SDL_VULKAN OR SDL_METAL OR SDL_RENDER_METAL)
-      set(ORIG_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
-      set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -ObjC")
-      check_c_source_compiles("
+      check_objc_source_compiles("
         #include <AvailabilityMacros.h>
         #import <Metal/Metal.h>
         #import <QuartzCore/CAMetalLayer.h>
@@ -2002,11 +2000,7 @@ elseif(APPLE)
         #if (!TARGET_CPU_X86_64 && !TARGET_CPU_ARM64)
         #error Metal doesn't work on this configuration
         #endif
-        int main(void) {
-            return 0;
-        }
-        " HAVE_FRAMEWORK_METAL)
-      set(CMAKE_REQUIRED_FLAGS ${ORIG_CMAKE_REQUIRED_FLAGS})
+        int main(void) {}" HAVE_FRAMEWORK_METAL)
       if(HAVE_FRAMEWORK_METAL)
         set(SDL_FRAMEWORK_METAL 1)
         set(SDL_FRAMEWORK_QUARTZCORE 1)