Fix shutdown because of Discord deinitializer

https://github.com/hrydgard/ppsspp/blob/f94beb518504eebadb94dfdc009cf9f4461bc6a4/UI/DiscordIntegration.cpp#L40
Calling exit(0) without NativeShutdown() breaks the assertion.

ios/ViewController.mm

@@ -213,7 +213,6 @@ static GraphicsContext *graphicsContext;
 			time_update();
 		}
 
-		threadStopped = true;
 
 		ILOG("Emulation thread shutting down\n");
 		NativeShutdownGraphics();
@@ -221,6 +220,8 @@ static GraphicsContext *graphicsContext;
 		// Also ask the main thread to stop, so it doesn't hang waiting for a new frame.
 		ILOG("Emulation thread stopping\n");
 		graphicsContext->StopThread();
+		
+		threadStopped = true;
 	});
 }
 

ios/main.mm

@@ -61,7 +61,10 @@ bool System_GetPropertyBool(SystemProperty prop) {
 
 void System_SendMessage(const char *command, const char *parameter) {
 	if (!strcmp(command, "finish")) {
-		exit(0);
+		dispatch_async(dispatch_get_main_queue(), ^{
+			[sharedViewController shutdown];
+			exit(0);
+		});
 	}
 }