SDL: Fixed compiling SDL_platform_defines.h on macOS with older compilers (thanks @sezero!) (8bc47)

From 8bc47dc3f155f4dd2f01b7f63ef32a45f620f70c Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Mon, 27 May 2024 14:33:18 -0700
Subject: [PATCH] Fixed compiling SDL_platform_defines.h on macOS with older
 compilers (thanks @sezero!)

Fixes #9632

(cherry picked from commit 36015ad5e58c413e8a101c48ed2bdbcdd044c868)
---
 include/SDL_platform.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/SDL_platform.h b/include/SDL_platform.h
index f9024d31b67fc..9bd753336ed4f 100644
--- a/include/SDL_platform.h
+++ b/include/SDL_platform.h
@@ -73,7 +73,13 @@
 #if defined(__APPLE__)
 /* lets us know what version of Mac OS X we're compiling on */
 #include <AvailabilityMacros.h>
+#ifndef __has_extension /* Older compilers don't support this */
+#define __has_extension(x) 0
 #include <TargetConditionals.h>
+#undef __has_extension
+#else
+#include <TargetConditionals.h>
+#endif
 
 /* Fix building with older SDKs that don't define these
    See this for more information: