Cross compiling: don't rewrite dirs if they're already prefixed....

build/linux/rewrite_dirs.py

 #!/usr/bin/python
 # Copyright (c) 2009 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.
 
 """Rewrites paths in -I, -L and other option to be relative to a sysroot."""
 
 import sys
 import os
 
 REWRITE_PREFIX = ['-I',
                   '-idirafter',
                   '-imacros',
                   '-imultilib',
                   '-include',
                   '-iprefix',
                   '-iquote',
                   '-isystem',
                   '-L']
 
 def RewritePath(path, sysroot):
   """Rewrites a path by prefixing it with the sysroot if it is absolute."""
-  if os.path.isabs(path):
+  if os.path.isabs(path) and not path.startswith(sysroot):
     path = path.lstrip('/')
     return os.path.join(sysroot, path)
   else:
     return path
 
 def RewriteLine(line, sysroot):
   """Rewrites all the paths in recognized options."""
   args = line.split()
   count = len(args)
   i = 0
@@ skipping 21 matching lines @@
     sys.stderr.write('usage: %s /path/to/sysroot\n' % argv[0])
     return 1
 
   for line in sys.stdin.readlines():
     line = RewriteLine(line.strip(), sysroot)
     print line
   return 0
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))