libretro: don't include getopt.h in configmanager

Check for __LIBRETRO__ before including getopt.h in ConfigManager.h,
because windows does not come with this header or function, and libretro
does not need it.

src/common/ConfigManager.h

@@ -8,10 +8,14 @@
 #ifndef __GNUC__
 #define HAVE_DECL_GETOPT 0
 #define __STDC__ 1
+#ifndef __LIBRETRO__
 #include "getopt.h"
+#endif
 #else // ! __GNUC__
 #define HAVE_DECL_GETOPT 1
+#ifndef __LIBRETRO__
 #include <getopt.h>
+#endif
 #endif // ! __GNUC__
 
 #define MAX_CHEATS 16384