SDL: remove warnings from Wundef in SDL_config.h.cmake

From bfbab5366084a2b21cd9ef65059bbf6b99b0f4a7 Mon Sep 17 00:00:00 2001
From: e <[EMAIL REDACTED]>
Date: Mon, 16 Aug 2021 23:07:30 -0300
Subject: [PATCH] remove warnings from Wundef in SDL_config.h.cmake

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

diff --git a/include/SDL_config.h.cmake b/include/SDL_config.h.cmake
index 23eb1205eb..0352922428 100644
--- a/include/SDL_config.h.cmake
+++ b/include/SDL_config.h.cmake
@@ -204,7 +204,7 @@
 #cmakedefine HAVE_POLL 1
 #cmakedefine HAVE__EXIT 1
 
-#elif __WIN32__
+#elif defined(__WIN32__)
 #cmakedefine HAVE_STDARG_H 1
 #cmakedefine HAVE_STDDEF_H 1
 #cmakedefine HAVE_FLOAT_H 1