Beginning work on GN build

build/toolchain/gcc_ar_wrapper.py

+#!/usr/bin/env python
+# 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.
+
+"""Runs the 'ar' command after removing its output file first.
+
+This script is invoked like:
+  python gcc_ar_wrapper.py --ar=$AR --output=$OUT $OP $INPUTS
+to do the equivalent of:
+  rm -f $OUT && $AR $OP $OUT $INPUTS
+"""
+
+import argparse
+import os
+import subprocess
+import sys
+
+
+# When running on a Windows host and using a toolchain whose tools are
+# actually wrapper scripts (i.e. .bat files on Windows) rather than binary
+# executables, the "command" to run has to be prefixed with this magic.
+# The GN toolchain definitions take care of that for when GN/Ninja is
+# running the tool directly.  When that command is passed in to this
+# script, it appears as a unitary string but needs to be split up so that
+# just 'cmd' is the actual command given to Python's subprocess module.
+BAT_PREFIX = 'cmd /c call '
+
+def CommandToRun(command):
+  if command[0].startswith(BAT_PREFIX):
+    command = command[0].split(None, 3) + command[1:]
+  return command
+
+
+def main():
+  parser = argparse.ArgumentParser(description=__doc__)
+  parser.add_argument('--ar',
+                      required=True,
+                      help='The ar binary to run',
+                      metavar='PATH')
+  parser.add_argument('--output',
+                      required=True,
+                      help='Output archive file',
+                      metavar='ARCHIVE')
+  parser.add_argument('--plugin',
+                      help='Load plugin')
+  parser.add_argument('operation',
+                      help='Operation on the archive')
+  parser.add_argument('inputs', nargs='+',
+                      help='Input files')
+  args = parser.parse_args()
+
+  command = [args.ar, args.operation]
+  if args.plugin is not None:
+    command += ['--plugin', args.plugin]
+  command.append(args.output)
+  command += args.inputs
+
+  # Remove the output file first.
+  try:
+    os.remove(args.output)
+  except OSError as e:
+    if e.errno != os.errno.ENOENT:
+      raise
+
+  # Now just run the ar command.
+  return subprocess.call(CommandToRun(command))
+
+
+if __name__ == "__main__":
+  sys.exit(main())