[NaCl SDK] Print nice error if host build can't find gcc or cl.exe

native_client_sdk/src/tools/oshelpers.py

 #!/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.
 
 import fnmatch
 import glob
 import optparse
 import os
 import posixpath
@@ skipping 451 matching lines @@
           print '  %s: %s (stored 0%%)' % (operation, zip_path)
         elif zip_info.compress_type == zipfile.ZIP_DEFLATED:
           print '  %s: %s (deflated %d%%)' % (operation, zip_path,
               100 - zip_info.compress_size * 100 / zip_info.file_size)
   finally:
     zip_stream.close()
 
   return 0
 
 
+def Which(args):
+  """A Unix style which.
+
+  Looks for all arguments in the PATH environment variable, and prints their
+  path if they are executable files.
+
+  Note: If you pass an argument with a path to which, it will just test if it
+  is executable, not if it is in the path.
+  """
+  parser = optparse.OptionParser(usage='usage: which args...')
+  _, files = parser.parse_args(args)
+  if not files:
+    return 0
+
+  env_path = os.environ.get('PATH', '')
+  paths = env_path.split(os.pathsep)
+
+  def IsExecutableFile(path):
+    return os.path.isfile(path) and os.access(path, os.X_OK)
+
+  retval = 0
+  for filename in files:
+    if os.path.sep in filename:
+      if IsExecutableFile(filename):
+        print filename
+        continue
+
+    for path in paths:
+      filepath = os.path.join(path, filename)
+      if IsExecutableFile(filepath):
+        print os.path.abspath(os.path.join(path, filename))
+        break
+    else:
+      retval = 1
+  return retval
+
+
 FuncMap = {
   'cp': Copy,
   'mkdir': Mkdir,
   'mv': Move,
   'rm': Remove,
   'zip': Zip,
+  'which': Which,
 }
 
 
 def main(args):
   if not args:
     print 'No command specified'
     print 'Available commands: %s' % ' '.join(FuncMap)
     return 1
   func = FuncMap.get(args[0])
   if not func:
     print 'Do not recognize command: ' + args[0]
     print 'Available commands: %s' % ' '.join(FuncMap)
     return 1
   return func(args[1:])
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))