POSIX: More Travis compile fixes

src/platforms/posix/work_queue/hrt_thread.c

@@ -63,7 +63,7 @@
  ****************************************************************************/
 
 /* The state of each work queue. */
-struct wqueue_s g_hrt_work = {};
+struct wqueue_s g_hrt_work;
 
 /****************************************************************************
  * Private Variables
@@ -265,6 +265,7 @@ static int work_hrtthread(int argc, char *argv[])
 void hrt_work_queue_init(void)
 {
 	px4_sem_init(&_hrt_work_lock, 0, 1);
+	memset(&g_hrt_work, 0, sizeof(g_hrt_work));
 
 	// Create high priority worker thread
 	g_hrt_work.pid = px4_task_spawn_cmd("wkr_hrt",