windowWillStartLiveResize: legacy OS compatibility fix

Author: jmroot

src/video/cocoa/SDL_cocoawindow.m

@@ -747,16 +747,26 @@ - (void)windowWillStartLiveResize:(NSNotification *)aNotification
 {
     // We'll try to maintain 60 FPS during live resizing
     const NSTimeInterval interval = 1.0 / 60.0;
+
+    const NSMethodSignature *invocationSig = [SDLWindow
+        instanceMethodSignatureForSelector:@selector(onLiveResizeTimerFire)];
+    NSInvocation *invocation = [NSInvocation
+        invocationWithMethodSignature:invocationSig];
+    [invocation setTarget:self];
+    [invocation setSelector:@selector(onLiveResizeTimerFire)];
+
     liveResizeTimer = [NSTimer scheduledTimerWithTimeInterval:interval
-                                                      repeats:TRUE
-                                                        block:^(NSTimer *unusedTimer)
-    {
-        SDL_OnWindowLiveResizeUpdate(_data.window);
-    }];
+                                                      invocation:invocation
+                                                      repeats:TRUE];
 
     [[NSRunLoop currentRunLoop] addTimer:liveResizeTimer forMode:NSRunLoopCommonModes];
 }
 
+- (void)onLiveResizeTimerFire
+{
+    SDL_OnWindowLiveResizeUpdate(_data.window);
+}
+
 - (void)windowDidEndLiveResize:(NSNotification *)aNotification
 {
     [liveResizeTimer invalidate];