GN: Fix compile errors with os==chromeos mojo/public build

build/config/linux/pkg-config.py

 # Copyright (c) 2013 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.
 
 import json
 import os
 import subprocess
 import sys
 import re
 from optparse import OptionParser
@@ skipping 83 matching lines @@
   if os.path.isabs(path) and not path.startswith(sysroot):
     if path.startswith(strip_prefix):
       path = path[len(strip_prefix):]
     path = path.lstrip('/')
     return os.path.join(sysroot, path)
   else:
     return path
 
 
 parser = OptionParser()
+parser.add_option('-p', action='store', dest='pkg_config', type='string',
+                  default='pkg-config')
 parser.add_option('-v', action='append', dest='strip_out', type='string')
 parser.add_option('-s', action='store', dest='sysroot', type='string')
 parser.add_option('-a', action='store', dest='arch', type='string')
 (options, args) = parser.parse_args()
 
 # Make a list of regular expressions to strip out.
 strip_out = []
 if options.strip_out != None:
   for regexp in options.strip_out:
     strip_out.append(re.compile(regexp))
 
 SetConfigPath(options)
 if options.sysroot:
   prefix = GetPkgConfigPrefixToStrip(args)
 else:
   prefix = ''
 
 try:
   flag_string = subprocess.check_output(
-      [ "pkg-config", "--cflags", "--libs-only-l", "--libs-only-L" ] +
+      [ options.pkg_config, "--cflags", "--libs-only-l", "--libs-only-L" ] +
       args, env=os.environ)
   # For now just split on spaces to get the args out. This will break if
   # pkgconfig returns quoted things with spaces in them, but that doesn't seem
   # to happen in practice.
   all_flags = flag_string.strip().split(' ')
 except:
   print "Could not run pkg-config."
   sys.exit(1)
 
 
@@ skipping 24 matching lines @@
     # this anyway. Removing it here prevents a bunch of duplicate inclusions on
     # the command line.
     pass
   else:
     cflags.append(flag)
 
 # Output a GN array, the first one is the cflags, the second are the libs. The
 # JSON formatter prints GN compatible lists when everything is a list of
 # strings.
 print json.dumps([includes, cflags, libs, lib_dirs, ldflags])