Fixed building with iOS SDK prior to 13.0

Fixes https://github.com/libsdl-org/SDL/pull/5045

src/joystick/iphoneos/SDL_mfijoystick.m

@@ -66,6 +66,9 @@ static NSString *GCInputXboxShareButton = @"Button Share";
 #if defined(__MACOSX__) && (__MAC_OS_X_VERSION_MAX_ALLOWED <= 101600)
 + (BOOL)supportsHIDDevice:(IOHIDDeviceRef)device;
 #endif
+#if !((__IPHONE_OS_VERSION_MAX_ALLOWED >= 130000) || (__APPLETV_OS_VERSION_MAX_ALLOWED >= 130000) || (__MAC_OS_VERSION_MAX_ALLOWED >= 1500000))
+@property(nonatomic, readonly) NSString *productCategory;
+#endif
 @end
 @interface GCExtendedGamepad (SDL)
 #if !((__IPHONE_OS_VERSION_MAX_ALLOWED >= 121000) || (__APPLETV_OS_VERSION_MAX_ALLOWED >= 121000) || (__MAC_OS_VERSION_MAX_ALLOWED >= 1401000))