Beginning work on GN build

build/toolchain/mac/setup_toolchain.py

+# 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.
+
+import os
+import stat
+import sys
+
+def CopyTool(source_path):
+  """Copies the given tool to the current directory, including a warning not
+  to edit it."""
+  with open(source_path) as source_file:
+    tool_source = source_file.readlines()
+
+  # Add header and write it out to the current directory (which should be the
+  # root build dir). Don't write the file if a matching file already exists
+  # because that causes a cascade of unnecessary rebuilds.
+  match = False
+  contents = ''.join([tool_source[0],
+                      '# Generated by setup_toolchain.py do not edit.\n']
+                     + tool_source[1:])
+  out_path = 'gyp-mac-tool'
+  try:
+    with open(out_path, 'rb') as read_tool_file:
+      existing_contents = read_tool_file.read()
+    if existing_contents == contents:
+      match = True
+  except:
+    pass
+  if not match:
+    with open(out_path, 'wb') as write_tool_file:
+      write_tool_file.write(contents)
+  st = os.stat(out_path)
+  if (st.st_mode & stat.S_IEXEC) == 0:
+    # Only chmod when necessary.
+    os.chmod(out_path, st.st_mode | stat.S_IEXEC)
+
+# Find the tool source, it's the first argument, and copy it.
+if len(sys.argv) != 2:
+  print "Need one argument (mac_tool source path)."
+  sys.exit(1)
+CopyTool(sys.argv[1])