More changes to support hermetic Xcode toolchain in GN.

third_party/WebKit/Source/build/scripts/gperf.py

 # Copyright 2014 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.
 
-# Invokes gperf for the GN build. The first argument is the path to gperf.
+# Invokes gperf for the GN build.
+# Usage: gperf.py [--developer_dir PATH_TO_XCODE] gperf ...

[Nico, 2016/10/10 19:35:59]

(fwiw you could use add_subparsers() to make sure that --developer-dir always
prependds gperf, but as-is is fine too

[erikchen, 2016/10/10 22:54:57]

noted. 

 # TODO(brettw) this can be removed once the run_executable rules have been
 # checked in for the GN build.
 
+import argparse
+import os
 import subprocess
 import sys
 
-subprocess.check_call(sys.argv[1:])
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--developer_dir", required=False)
+    args, unknownargs = parser.parse_known_args()
+    if args.developer_dir:
+        os.environ['DEVELOPER_DIR'] = args.developer_dir
+
+    subprocess.check_call(unknownargs)
+
+if __name__ == '__main__':
+    main()