Control the order of gclient spec keys in fetch

fetch.py

 #!/usr/bin/env python
 # Copyright (c) 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.
 
 """
 Tool to perform checkouts in one easy command line!
 
 Usage:
   fetch <recipe> [--property=value [--property2=value2 ...]]
@@ skipping 84 matching lines @@
     return self.run((svn_path,) + cmd, **kwargs)
 
 
 class GclientGitCheckout(GclientCheckout, GitCheckout):
 
   def __init__(self, dryrun, spec, root):
     super(GclientGitCheckout, self).__init__(dryrun, spec, root)
     assert 'solutions' in self.spec
     keys = ['solutions', 'target_os', 'target_os_only']
     gclient_spec = '\n'.join('%s = %s' % (key, self.spec[key])
-                             for key in self.spec if key in keys)
+                             for key in keys if key in self.spec)
     self.spec['gclient_spec'] = gclient_spec
 
   def exists(self):
     return os.path.exists(os.path.join(os.getcwd(), self.root))
 
   def init(self):
     # TODO(dpranke): Work around issues w/ delta compression on big repos.
     self.run_git('config', '--global', 'core.deltaBaseCacheLimit', '1G')
 
     # Configure and do the gclient checkout.
@@ skipping 153 matching lines @@
 
 
 def main():
   dryrun, recipe, props = handle_args(sys.argv)
   spec, root = run_recipe_fetch(recipe, props)
   return run(dryrun, spec, root)
 
 
 if __name__ == '__main__':
   sys.exit(main())