make `python build/vs_toolchain.py update` work a bit better on non-windows

win_toolchain/get_toolchain_if_necessary.py

 #!/usr/bin/env python
 # Copyright 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.
 
 """Downloads and unpacks a toolchain for building on Windows. The contents are
 matched by sha1 which will be updated when the toolchain is updated.
 
 Having a toolchain script in depot_tools means that it's not versioned
 directly with the source code. That is, if the toolchain is upgraded, but
@@ skipping 110 matching lines @@
       return True
     return subprocess.call(
         ['git', '-c', 'core.askpass=true', 'remote', 'show',
          'https://chrome-internal.googlesource.com/chrome/src-internal/'],
         shell=True, stdin=nul, stdout=nul, stderr=nul) == 0
 
 
 def LooksLikeGoogler():
   """Checks for a USERDOMAIN environment variable of 'GOOGLE', which
   probably implies the current user is a Googler."""
-  return os.environ.get('USERDOMAIN').upper() == 'GOOGLE'
+  return os.environ.get('USERDOMAIN', '').upper() == 'GOOGLE'
 
 
 def CanAccessToolchainBucket():
   """Checks whether the user has access to gs://chrome-wintoolchain/."""
   gsutil = download_from_google_storage.Gsutil(
       download_from_google_storage.GSUTIL_DEFAULT_PATH, boto_path=None)
   code, _, _ = gsutil.check_call('ls', 'gs://chrome-wintoolchain/')
   return code == 0
 
 
@@ skipping 41 matching lines @@
   assert os.path.basename(filename) == filename
   target_path = os.path.join(temp_dir, filename)
   gsutil = download_from_google_storage.Gsutil(
       download_from_google_storage.GSUTIL_DEFAULT_PATH, boto_path=None)
   code = gsutil.call('cp', 'gs://chrome-wintoolchain/' + filename, target_path)
   if code != 0:
     sys.exit('gsutil failed')
   return temp_dir, target_path
 
 
+def RmDir(path):
+  """Deletes path and all the files it contains."""
+  if sys.platform != 'win32':
+    shutil.rmtree(path, ignore_errors=True)
+  else:
+    # shutil.rmtree() doesn't delete read-only files on Windows.
+    subprocess.check_call('rmdir /s/q "%s"' % path, shell=True)
+
+
 def DoTreeMirror(target_dir, tree_sha1):
   """In order to save temporary space on bots that do not have enough space to
   download ISOs, unpack them, and copy to the target location, the whole tree
   is uploaded as a zip to internal storage, and then mirrored here."""
   temp_dir, local_zip = DownloadUsingGsutil(tree_sha1 + '.zip')
   sys.stdout.write('Extracting %s...\n' % local_zip)
   sys.stdout.flush()
   with zipfile.ZipFile(local_zip, 'r', zipfile.ZIP_DEFLATED, True) as zf:
     zf.extractall(target_dir)
   if temp_dir:
-    subprocess.check_call('rmdir /s/q "%s"' % temp_dir, shell=True)
+    RmDir(temp_dir)
 
 
 def main():
   if not sys.platform.startswith(('cygwin', 'win32')):
     return 0
 
   parser = optparse.OptionParser(description=sys.modules[__name__].__doc__)
   parser.add_option('--output-json', metavar='FILE',
                     help='write information about toolchain to FILE')
   options, args = parser.parse_args()
 
   if sys.platform == 'cygwin':
     # This script requires Windows Python, so invoke with depot_tools' Python.
     def winpath(path):
       return subprocess.check_output(['cygpath', '-w', path]).strip()
     python = os.path.join(DEPOT_TOOLS_PATH, 'python.bat')
     cmd = [python, winpath(__file__)]
     if options.output_json:
       cmd.extend(['--output-json', winpath(options.output_json)])
     cmd.extend(args)
     sys.exit(subprocess.call(cmd))
+  assert sys.platform != 'cygwin'
 
   # We assume that the Pro hash is the first one.
   desired_hashes = args
   if len(desired_hashes) == 0:
     sys.exit('Desired hashes are required.')
 
   # Move to depot_tools\win_toolchain where we'll store our files, and where
   # the downloader script is.
   os.chdir(os.path.normpath(os.path.join(BASEDIR)))
   toolchain_dir = '.'
@@ skipping 21 matching lines @@
     if not should_use_gs:
       print('Please follow the instructions at '
             'http://www.chromium.org/developers/how-tos/'
             'build-instructions-windows')
       return 1
     print('Windows toolchain out of date or doesn\'t exist, updating (Pro)...')
     print('  current_hash: %s' % current_hash)
     print('  desired_hashes: %s' % ', '.join(desired_hashes))
     sys.stdout.flush()
     DelayBeforeRemoving(target_dir)
-    # This stays resident and will make the rmdir below fail.
-    with open(os.devnull, 'wb') as nul:
-      subprocess.call(['taskkill', '/f', '/im', 'mspdbsrv.exe'],
-                      stdin=nul, stdout=nul, stderr=nul)
+    if sys.platform == 'win32':
+      # This stays resident and will make the rmdir below fail.
+      with open(os.devnull, 'wb') as nul:
+        subprocess.call(['taskkill', '/f', '/im', 'mspdbsrv.exe'],
+                        stdin=nul, stdout=nul, stderr=nul)
     if os.path.isdir(target_dir):
-      subprocess.check_call('rmdir /s/q "%s"' % target_dir, shell=True)
+      RmDir(target_dir)
 
     DoTreeMirror(target_dir, desired_hashes[0])
 
     got_new_toolchain = True
 
   win_sdk = os.path.join(abs_target_dir, 'win_sdk')
   try:
     with open(os.path.join(target_dir, 'VS_VERSION'), 'rb') as f:
       vs_version = f.read().strip()
   except IOError:
@@ skipping 29 matching lines @@
 
   if options.output_json:
     shutil.copyfile(os.path.join(target_dir, '..', 'data.json'),
                     options.output_json)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())