cmake: Fix Metal detection on macOS/iOS. Apparently the "-x objective-c" made it down to the linker, who then treats the .o file as Objective-C source code. Apparently the -ObjC argument does the same thing but gets ignored by the linker. Fixes Bugzilla #4988.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index b703c34..33d5055 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1742,7 +1742,7 @@ elseif(APPLE)
if(VIDEO_VULKAN OR VIDEO_METAL OR RENDER_METAL)
set(ORIG_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
- set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -x objective-c")
+ set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -ObjC")
check_c_source_compiles("
#include <AvailabilityMacros.h>
#import <Metal/Metal.h>