Add buildbot scripts for GN builders and dartdevc testers

tools/bots/gn_tests.py

+#!/usr/bin/env python
+#
+# Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+import os
+import os.path
+import shutil
+import sys
+import subprocess
+
+import bot
+import bot_utils
+
+utils = bot_utils.GetUtils()
+
+BUILD_OS = utils.GuessOS()
+
+(bot_name, _) = bot.GetBotName()
+CHANNEL = bot_utils.GetChannelFromName(bot_name)
+
+if __name__ == '__main__':
+  print "This step should test the sdk that was built using gn"
+  print "Current directory when running on a bot should be"
+  print "/b/build/slave/[builder name]/build/sdk"
+