Fixed warnings when building with cygwin

Fixes https://github.com/libsdl-org/SDL/issues/5025

src/events/SDL_events.c

@@ -35,7 +35,7 @@
 #include "SDL_syswm.h"
 
 #undef SDL_PRIs64
-#ifdef __WIN32__
+#if defined(__WIN32__) && !defined(__CYGWIN__)
 #define SDL_PRIs64  "I64d"
 #else
 #define SDL_PRIs64  "lld"