SDL: Fixed building on older macOS SDKs

From edc8f0b8412d968d14bc40cfd2086e0d345cb8c8 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Fri, 10 Mar 2023 16:15:46 -0800
Subject: [PATCH] Fixed building on older macOS SDKs

---
 src/video/cocoa/SDL_cocoaevents.m | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/video/cocoa/SDL_cocoaevents.m b/src/video/cocoa/SDL_cocoaevents.m
index a2823343ff0e..d84e708c9e82 100644
--- a/src/video/cocoa/SDL_cocoaevents.m
+++ b/src/video/cocoa/SDL_cocoaevents.m
@@ -27,6 +27,7 @@
 
 #ifndef MAC_OS_X_VERSION_10_12
 #define NSEventTypeApplicationDefined NSApplicationDefined
+typedef NSString *NSKeyValueChangeKey;
 #endif
 
 static SDL_Window *FindSDLWindowForNSWindow(NSWindow *win)