Make use_system_mesa switch work: make symlinks

for nacl untrusted build.

BUG=161389

Review URL: https://codereview.chromium.org/11862016

git-svn-id: http://src.chromium.org/svn/trunk/src/build@178028 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

symlink.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python
+# Copyright (c) 2013 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.
+
+"""Make a symlink and optionally touch a file (to handle dependencies)."""
+
+
+import errno
+import optparse
+import os.path
+import sys
+
+
+def Main(argv):
+  parser = optparse.OptionParser()
+  parser.add_option('-f', '--force', action='store_true')
+  parser.add_option('--touch')
+
+  options, args = parser.parse_args(argv)
+  if len(args) < 2:
+    parser.error('at least two arguments required.')
+
+  target = args[-1]
+  sources = args[:-1]
+  for s in sources:
+    t = os.path.join(target, os.path.basename(s))
+    try:
+      os.symlink(s, t)
+    except OSError, e:
+      if e.errno == errno.EEXIST and options.force:
+        os.remove(t)
+        os.symlink(s, t)
+      else:
+        raise
+
+
+  if options.touch:
+    with open(options.touch, 'w') as f:
+      pass
+
+
+if __name__ == '__main__':
+  sys.exit(Main(sys.argv))