SDL: Guard against _USE_MATH_DEFINES redefinition

From a23d1af0ac13f4ddd408a75b7e82b58ec307beb0 Mon Sep 17 00:00:00 2001
From: Knightly <[EMAIL REDACTED]>
Date: Fri, 10 Feb 2023 19:23:59 -1000
Subject: [PATCH] Guard against _USE_MATH_DEFINES redefinition

---
 include/SDL_stdinc.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/SDL_stdinc.h b/include/SDL_stdinc.h
index bbce3d06f110..20997831acee 100644
--- a/include/SDL_stdinc.h
+++ b/include/SDL_stdinc.h
@@ -85,7 +85,9 @@
    Visual Studio.  See http://msdn.microsoft.com/en-us/library/4hwaceh6.aspx
    for more information.
 */
-#  define _USE_MATH_DEFINES
+#  ifndef _USE_MATH_DEFINES
+#    define _USE_MATH_DEFINES
+#  endif
 # endif
 # include <math.h>
 #endif