mingw-w64-headers: bump _mingw_mac.h to 9.0.0

Signed-off-by: Jonathan Yong <10walls@gmail.com>
diff --git a/mingw-w64-headers/crt/_mingw_mac.h b/mingw-w64-headers/crt/_mingw_mac.h
index add6eb8..4160013 100644
--- a/mingw-w64-headers/crt/_mingw_mac.h
+++ b/mingw-w64-headers/crt/_mingw_mac.h
@@ -11,7 +11,7 @@
 #define __MINGW64_STRINGIFY(x) \
   __STRINGIFY(x)
 
-#define __MINGW64_VERSION_MAJOR 8
+#define __MINGW64_VERSION_MAJOR 9
 #define __MINGW64_VERSION_MINOR 0
 #define __MINGW64_VERSION_BUGFIX 0