Provide IRT process interface

src/untrusted/nacl/setpgid.c

 /*
  * Copyright (c) 2013 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.
  */
 
 #include <errno.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include "native_client/src/untrusted/nacl/nacl_irt.h"
 
-int chdir(const char *path) {
-  if (!__libnacl_irt_init_fn(&__libnacl_irt_dev_filename.chdir,
-                             __libnacl_irt_dev_filename_init)) {
+int setpgid(pid_t pid, pid_t pgid) {
+  if (!__libnacl_irt_init_fn(&__libnacl_irt_dev_process.setpgid,
+                             __libnacl_irt_dev_process_init)) {
     return -1;
   }
 
-  int error = __libnacl_irt_dev_filename.chdir(path);
+  int error = __libnacl_irt_dev_process.setpgid(pid, pgid);
   if (error) {
     errno = error;
     return -1;
   }
 
   return 0;
 }