Use _MSC_VER for MSVC-specific pragmas

These aren't used on mingw so they need to be surrounded by #ifdef
_MSC_VER

plugins/win-capture/graphics-hook/gl-capture.c

@@ -1,6 +1,10 @@
 #define _CRT_SECURE_NO_WARNINGS
+
+#ifdef _MSC_VER
 #pragma warning(disable : 4214) /* nonstandard extension, non-int bitfield */
 #pragma warning(disable : 4054) /* function pointer to data pointer */
+#endif
+
 #include <windows.h>
 
 #define COBJMACROS

plugins/win-capture/graphics-hook/graphics-hook.h

@@ -1,7 +1,9 @@
 #pragma once
 
+#ifdef _MSC_VER
 /* conversion from data/function pointer */
 #pragma warning(disable: 4152)
+#endif
 
 #include "../graphics-hook-info.h"