Don't modify the PWD in gyp_v8

build/gyp_v8

 #!/usr/bin/env python
 #
 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 18 matching lines @@
 
 # This script is wrapper for V8 that adds some support for how GYP
 # is invoked by V8 beyond what can be done in the gclient hooks.
 
 import glob
 import os
 import platform
 import shlex
 import sys
 
-script_dir = os.path.dirname(__file__)
-v8_root = os.path.normpath(os.path.join(script_dir, os.pardir))
-
-if __name__ == '__main__':
-  os.chdir(v8_root)
-  script_dir = os.path.dirname(__file__)
-  v8_root = '.'
+script_dir = os.path.dirname(os.path.realpath(__file__))
+v8_root = os.path.abspath(os.path.join(script_dir, os.pardir))
 
 sys.path.insert(0, os.path.join(v8_root, 'build', 'gyp', 'pylib'))
 import gyp
 
 # Add paths so that pymod_do_main(...) can import files.
 sys.path.insert(
     1, os.path.abspath(os.path.join(v8_root, 'tools', 'generate_shim_headers')))
 
 
 def apply_gyp_environment(file_path=None):
@@ skipping 79 matching lines @@
 
   # If we didn't get a file, check an env var, and then fall back to
   # assuming 'all.gyp' from the same directory as the script.
   if not gyp_file_specified:
     gyp_file = os.environ.get('V8_GYP_FILE')
     if gyp_file:
       # Note that V8_GYP_FILE values can't have backslashes as
       # path separators even on Windows due to the use of shlex.split().
       args.extend(shlex.split(gyp_file))
     else:
-      # Note that this must not start with "./" or things break.
-      # So we rely on having done os.chdir(v8_root) above and use the
-      # relative path.
-      args.append(os.path.join('build', 'all.gyp'))
+      args.append(os.path.join(script_dir, 'all.gyp'))
 
   args.extend(['-I' + i for i in additional_include_files(args)])
 
   # There shouldn't be a circular dependency relationship between .gyp files
   args.append('--no-circular-check')
 
   # Set the GYP DEPTH variable to the root of the V8 project.
   args.append('--depth=' + v8_root)
 
   # If V8_GYP_SYNTAX_CHECK is set to 1, it will invoke gyp with --check
   # to enfore syntax checking.
   syntax_check = os.environ.get('V8_GYP_SYNTAX_CHECK')
   if syntax_check and int(syntax_check):
     args.append('--check')
 
   print 'Updating projects from gyp files...'
   sys.stdout.flush()
 
   # Generate for the architectures supported on the given platform.
   gyp_args = list(args)
   if platform.system() == 'Linux':
     # --generator-output defines where the Makefile goes.
     gyp_args.append('--generator-output=out')
     # -Goutput_dir defines where the build output goes, relative to the
     # Makefile. Set it to . so that the build output doesn't end up in out/out.
     gyp_args.append('-Goutput_dir=.')
   run_gyp(gyp_args)