Use `__builtin_setjmp()`, `__builtin_longjmp()` on MinGW; fix
@@ -35,6 +35,9 @@ typedef mrb_int mrb_jmpbuf_impl;
#if defined(__APPLE__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)
#define MRB_SETJMP _setjmp
#define MRB_LONGJMP _longjmp
+#elif defined(__MINGW64__) && defined(__GNUC__) && __GNUC__ >= 4
+#define MRB_SETJMP __builtin_setjmp
+#define MRB_LONGJMP __builtin_longjmp
#else
#define MRB_SETJMP setjmp
#define MRB_LONGJMP longjmp
