SDL: Make sure Objective C files are built with the same flags as C files.

SDL Commits
1 
From 6da6a6cba2a7c857890063073f47445584617bcb Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Sat, 21 May 2022 13:51:21 -0700
Subject: [PATCH] Make sure Objective C files are built with the same flags as
 C files.

Fixes https://github.com/libsdl-org/SDL/issues/5707
---
 CMakeLists.txt | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2ce31aba84e..8e2832fa032 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3122,3 +3122,6 @@ endif()
 if(SDL_TEST)
   add_subdirectory(test)
 endif()
+
+##### Fix Objective C builds #####
+set(CMAKE_OBJC_FLAGS "${CMAKE_OBJC_FLAGS} ${CMAKE_C_FLAGS}")