vxlib.c (__gthread_once): Add missing value to nested return statement.

2017-06-02  Olivier Hainque  <hainque@adacore.com>

	* config/vxlib.c (__gthread_once): Add missing value to
	nested return statement.

From-SVN: r248838

libgcc/config/vxlib.c

@@ -70,7 +70,7 @@ __gthread_once (__gthread_once_t *guard, void (*func)(void))
       /* This can happen on powerpc, which is using all 32 bits
 	 of the gthread_once_t structure.  */
       if (guard->done)
-	return;
+	return 0;
 #endif
       taskDelay (1);
     }