GN: Autodetect Visual Studio versions

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 140 matching lines @@
   ]
   for i in remap_cases:
     if i[0] in vars_dict and vars_dict[i[0]] == i[1]:
       gn_args += ' ' + i[2]
 
   # These string arguments get passed directly.
   for v in ['windows_sdk_path']:
     if v in vars_dict:
       gn_args += ' ' + v + '=' + EscapeStringForGN(vars_dict[v])
 
+  # Some other flags come from GYP environment variables.
+  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_override_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'
   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.
@@ skipping 168 matching lines @@
   # to enfore syntax checking.
   syntax_check = os.environ.get('CHROMIUM_GYP_SYNTAX_CHECK')
   if syntax_check and int(syntax_check):
     args.append('--check')
 
   print 'Updating projects from gyp files...'
   sys.stdout.flush()
 
   # Off we go...
   sys.exit(gyp.main(args))