Support -Goutput_dir=blahblah in GN-GYP hybrid mode

build/gyp_chromium

 #!/usr/bin/env python
 
 # Copyright (c) 2012 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.
 
 # This script is wrapper for Chromium that adds some support for how GYP
 # is invoked by Chromium beyond what can be done in the gclient hooks.
 
 import glob
@@ skipping 109 matching lines @@
   # GYP defines from the command line. We can't use optparse since we want
   # to ignore all arguments other than "-D".
   cmdline_input_items = []
   for i in range(len(sys.argv))[1:]:
     if sys.argv[i] == '-D' and i + 1 < len(sys.argv):
       cmdline_input_items += [sys.argv[i + 1]]
   cmdline_items = ProcessGypDefinesItems(cmdline_input_items)
 
   return dict(supp_items + env_items + cmdline_items)
 
+def GetOutputDirectory():
+  """Returns the output directory that GYP will use."""
+  # GYP generator flags from the command line. We can't use optparse since we
+  # want to ignore all arguments other than "-G".
+  needle = '-Goutput_dir='
+  cmdline_input_items = []
+  for item in sys.argv[1:]:
+    if item.startswith(needle):
+      return item[len(needle):]
+
+  env_items = shlex.split(os.environ.get('GYP_GENERATOR_FLAGS', ''))
+  needle = 'output_dir='
+  for item in env_items:
+    if item.startswith(needle):
+      return item[len(needle):]
+
+  return "out"
 
 def GetArgsStringForGN(supplemental_files):
   """Returns the args to pass to GN.
   Based on a subset of the GYP variables that have been rewritten a bit."""
 
   # Find the .gyp directory in the user's home directory.
   home_dot_gyp = os.environ.get('GYP_CONFIG_DIR', None)
   if home_dot_gyp:
     home_dot_gyp = os.path.expanduser(home_dot_gyp)
   if not home_dot_gyp:
@@ skipping 77 matching lines @@
   gyp_msvs_version = os.environ.get('GYP_MSVS_VERSION', '')
   if gyp_msvs_version:
     gn_args += ' visual_studio_version=' + EscapeStringForGN(gyp_msvs_version)
   gyp_msvs_override_path = os.environ.get('GYP_MSVS_OVERRIDE_PATH', '')
   if gyp_msvs_override_path:
     gn_args += ' visual_studio_path=' + \
         EscapeStringForGN(gyp_msvs_override_path)
 
   # Set the GYP flag so BUILD files know they're being invoked in GYP mode.
   gn_args += ' is_gyp=true'
+
+  gyp_outdir = GetOutputDirectory()
+  gn_args += ' gyp_output_dir=\"%s\"' % gyp_outdir
+
   return gn_args.strip()
 
 
 def additional_include_files(supplemental_files, args=[]):
   """
   Returns a list of additional (.gypi) files to include, without duplicating
   ones that are already specified on the command line. The list of supplemental
   include files is passed in as an argument.
   """
   # Determine the include files specified on the command line.
@@ skipping 40 matching lines @@
     print 'Unknown platform for GN: ', sys.platform
     return False
 
   print 'Generating gyp files from GN...'
 
   # Need to pass both the source root (the bots don't run this command from
   # within the source tree) as well as set the is_gyp value so the BUILD files
   # to know they're being run under GYP.
   args = [gnpath, 'gyp', '-q',
           '--root=' + chrome_src,
-          '--args=' + GetArgsStringForGN(supplemental_includes)]
+          '--args=' + GetArgsStringForGN(supplemental_includes),
+          '--output=//' + GetOutputDirectory() + '/gn_build/']
   return subprocess.call(args) == 0
 
 
 if __name__ == '__main__':
   args = sys.argv[1:]
 
   if int(os.environ.get('GYP_CHROMIUM_NO_ACTION', 0)):
     print 'Skipping gyp_chromium due to GYP_CHROMIUM_NO_ACTION env var.'
     sys.exit(0)
 
@@ skipping 92 matching lines @@
   syntax_check = os.environ.get('CHROMIUM_GYP_SYNTAX_CHECK')
   if syntax_check and int(syntax_check):
     args.append('--check')
 
   supplemental_includes = GetSupplementalFiles()
   if not RunGN(supplemental_includes):
     sys.exit(1)
   args.extend(
       ['-I' + i for i in additional_include_files(supplemental_includes, args)])
 
+  args.extend(['-D', 'gyp_output_dir=' + GetOutputDirectory()])
+
   print 'Updating projects from gyp files...'
   sys.stdout.flush()
 
   # Off we go...
   sys.exit(gyp.main(args))