Split parts of //chrome/utility's BUILD.gn into //chrome/utility/safe_browsing/mac.

chrome/utility/safe_browsing/mac/crdmg.cc

 // Copyright 2015 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.
 
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
 #include <sandbox.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
 
 #include <string>
 
 #include "base/files/file.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/utility/safe_browsing/mac/hfs.h"
 #include "chrome/utility/safe_browsing/mac/read_stream.h"
 #include "chrome/utility/safe_browsing/mac/udif.h"
 
+// This executable only works on 10.10+, so unconditionally use these functions
+// to make sandboxing easier.
+extern "C" {
+int mkdirat(int, const char *, mode_t);
+int openat(int, const char *, int, ...);
+int unlinkat(int, const char *, int);
+}
+
 namespace {
 
 // SafeDMG (crdmg) is a utility that can perform a list or extract operation
 // for DMG files. It does so without using the OS X built-in support for DMG
 // files, and it operates under a restrictive sandbox. This is suitable for
 // examining DMG files of untrusted origins.
 //
 // Usage: crdmg file.dmg [unpack-path]
 // If unpack-path is provided, it will extract the contents of file.dmg to the
 // directory, creating it if it does not exit. Otherwise, it will merely list
@@ skipping 210 matching lines @@
 
   return true;
 }
 
 }  // namespace
 
 int main(int argc, const char* argv[]) {
   SafeDMG safe_dmg;
   return safe_dmg.Main(argc, argv);
 }