Share the zygote's fopen overrides with nacl_helper.

sandbox/sandbox_linux.gypi

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'targets': [
     # We have two principal targets: sandbox and sandbox_linux_unittests
     # All other targets are listed as dependencies.
     # FIXME(jln): for historial reasons, sandbox_linux is the setuid sandbox
     # and is its own target.
@@ skipping 68 matching lines @@
         'linux/suid/sandbox.c',
       ],
       'cflags': [
         # For ULLONG_MAX
         '-std=gnu99',
       ],
       'include_dirs': [
         '..',
       ],
     },
+    {
+      'target_name': 'libc_urandom_override',
+      'type': 'static_library',
+      'sources': [
+        'linux/services/libc_urandom_override.cc',
+        'linux/services/libc_urandom_override.h',
+      ],
+      'dependencies': [
+        '../base/base.gyp:base',
+      ],
+      'include_dirs': [
+        '..',
+      ],
+    },
   ],
 }