allow gyp_skia to be run from any directory.

gyp_skia

 #!/usr/bin/python
 
 # Copyright 2011 The Android Open Source Project
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This script is a wrapper which invokes gyp with the correct --depth argument,
 # and supports the automatic regeneration of build files if all.gyp is
 # changed (Linux-only).
 
 import glob
 import os
 import platform
 import shlex
 import sys
 
-script_dir = os.path.dirname(__file__)
+script_dir = os.path.abspath(os.path.dirname(__file__))
 
 # Directory within which we can find the gyp source.
 gyp_source_dir = os.path.join(script_dir, 'third_party', 'externals', 'gyp')
 
 # Directory within which we can find most of Skia's gyp configuration files.
 gyp_config_dir = os.path.join(script_dir, 'gyp')
 
 # Ensure we import our current gyp source's module, not any version
 # pre-installed in your PYTHONPATH.
 sys.path.insert(0, os.path.join(gyp_source_dir, 'pylib'))
@@ skipping 97 matching lines @@
   args.extend(['-Goutput_dir=.'])
 
   # By default, we build 'most' instead of 'all' or 'everything'. See skia.gyp.
   args.extend(['-Gdefault_target=most'])
 
   print 'Updating projects from gyp files...'
   sys.stdout.flush()
 
   # Off we go...
   sys.exit(gyp.main(args))