Add platform_utils and stub test lists for Linux.

webkit/tools/layout_tests/layout_package/platform_utils.py

 #!/bin/env python
 # Copyright (c) 2006-2008 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.
 
 """Platform-specific utilities and pseudo-constants
 
 Any functions whose implementations or values differ from one platform to
 another should be defined in their respective platform_utils_<platform>.py
 modules. The appropriate one of those will be imported into this module to
 provide callers with a common, platform-independent interface.
 """
 
 import sys
 
 # We may not support the version of Python that a user has installed (Cygwin
 # especially has had problems), but we'll allow the platform utils to be
 # included in any case so we don't get an import error.
 if sys.platform in ('cygwin', 'win32'):
   from platform_utils_win import *
 elif sys.platform == 'darwin':
   from platform_utils_mac import *
-
-
+elif sys.platform in ('linux', 'linux2'):
+  from platform_utils_linux import *