Fix runit.py script on windows.

scripts/tools/runit.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.
 
 """Runs a command with PYTHONPATH set up for the Chromium build setup.
 
 This is helpful for running scripts locally on a development machine.
 
 Try `scripts/common/runit.py python`
@@ skipping 68 matching lines @@
     option_parser.error('Must provide a command to run.')
 
   path = os.environ.get('PYTHONPATH', '').split(os.pathsep)
   add_build_paths(path)
   os.environ['PYTHONPATH'] = os.pathsep.join(path)
 
   if options.show_path:
     print 'Set PYTHONPATH: %s' % os.environ['PYTHONPATH']
 
   # Use subprocess instead of execv because otherwise windows destroys quoting.
-  p = subprocess.Popen(args)
+  p = subprocess.Popen([sys.executable] + args)
   p.wait()
   return p.returncode
 
 
 if __name__ == '__main__':
   sys.exit(main())