XQuartz: Mark functions _X_NORETURN

Signed-off-by: Jeremy Huddleston <jeremyhu@apple.com>

hw/xquartz/darwin.c

@@ -772,8 +772,8 @@ void ddxGiveUp( void )
  *      made to restore all original setting of the displays. Also all devices
  *      are closed.
  */
-void AbortDDX( void )
-{
+_X_NORETURN
+void AbortDDX( void ) {
     ErrorF( "   AbortDDX\n" );
     OsAbort();
 }

hw/xquartz/mach-startup/stub.c

@@ -164,6 +164,7 @@ static void send_fd_handoff(int connected_fd, int launchd_fd) {
     close(connected_fd);
 }
 
+__attribute__((__noreturn__))
 static void signal_handler(int sig) {
     if(x11app_pid)
         kill(x11app_pid, sig);

hw/xquartz/quartzStartup.c

@@ -56,6 +56,7 @@ struct arg {
     char **envp;
 };
 
+_X_NORETURN
 static void server_thread (void *arg) {
     struct arg args = *((struct arg *)arg);
     free(arg);