Fix build on Clang < 12

SetFlags.cmake

@@ -158,7 +158,7 @@ function(set_exe_flags TARGET)
 			# TODO: actually fix the warnings instead of disabling them
 			# or at least disable on a file-level basis:
 			-Wno-missing-noreturn -Wno-padded -Wno-implicit-fallthrough
-			-Wno-double-promotion -Wno-reserved-identifier
+			-Wno-double-promotion
 
 			# This is a pretty useless warning, we've already got -Wswitch which is what we need:
 			-Wno-switch-enum
@@ -186,5 +186,14 @@ function(set_exe_flags TARGET)
 				-Wno-implicit-int-float-conversion
 			)
 		endif()
+
+		if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 13)
+			target_compile_options(
+				${TARGET} PRIVATE
+
+				# TODO: fix
+				-Wno-reserved-identifier
+			)
+		endif()
 	endif()
 endfunction()