Make libnosys function stubs part of libnacl

src/untrusted/nacl/stubs/vfork-stub.c

 /*
  * Copyright 2010 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can
  * be found in the LICENSE file.
  */
 
 
 /*
  * Stub routine for `vfork' for porting support.
  */
 
 #include <sys/types.h>
 #include <unistd.h>
 #include <errno.h>
 
 pid_t vfork(void) {
   errno = ENOSYS;
   return -1;
 }
-
-#include "native_client/src/untrusted/nosys/warning.h"
-stub_warning(vfork);