SDL: avoid -Wundef warning from SDL_config_windows.h

SDL Commits
1 
From bfdea6057252e0aedaccd6e8fcee899c8f976bb6 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Sat, 26 Jun 2021 05:56:10 +0300
Subject: [PATCH] avoid -Wundef warning from SDL_config_windows.h

---
 include/SDL_config_windows.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/SDL_config_windows.h b/include/SDL_config_windows.h
index bed9d42ec..1c838f856 100644
--- a/include/SDL_config_windows.h
+++ b/include/SDL_config_windows.h
@@ -195,7 +195,7 @@ typedef unsigned int uintptr_t;
 #endif
 
 /* Check to see if we have Windows 10 build environment */
-#if _MSC_VER >= 1911        /* Visual Studio 15.3 */
+#if defined(_MSC_VER) && (_MSC_VER >= 1911)        /* Visual Studio 15.3 */
 #include <sdkddkver.h>
 #if _WIN32_WINNT >= 0x0601  /* Windows 7 */
 #define SDL_WINDOWS7_SDK