Die out autotest script if there is no board parameter specified.

src/scripts/autotest

 #!/usr/bin/python
 
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # A python wrapper to call autotest ebuild.
 
 import commands, logging, optparse, os, subprocess, sys
 
@@ skipping 195 matching lines @@
 
 
 def main():
   me = sys.argv[0]
   common_sh = os.path.join(os.path.dirname(me), 'common.sh')
 
   assert_inside_chroot(common_sh)
   set_common_env(common_sh, 'GCLIENT_ROOT')
 
   options, args = parse_args_and_help()
+
+  if not options.board:
+    die(common_sh, 'Missing --board argument.')
+
   if options.build:
     status = build_autotest(options)
     if status:
       die(common_sh, 'build_autotest failed.')
   else:
     ssh_key_file = os.path.join(os.path.dirname(me),
                                 'mod_for_test_scripts/ssh_keys/testing_rsa')
     os.chmod(ssh_key_file, 0400)
     run_autoserv(options, args)
 
 
 if __name__ == '__main__':
   main()