Move RunGN lower so that modifications to os.environ take effect

build/gyp_chromium

 #!/usr/bin/env python
 
 # Copyright (c) 2012 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.
 
 # This script is wrapper for Chromium that adds some support for how GYP
 # is invoked by Chromium beyond what can be done in the gclient hooks.
 
 import glob
@@ skipping 285 matching lines @@
   # assuming 'all.gyp' from the same directory as the script.
   if not gyp_file_specified:
     gyp_file = os.environ.get('CHROMIUM_GYP_FILE')
     if gyp_file:
       # Note that CHROMIUM_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:
       args.append(os.path.join(script_dir, 'all.gyp'))
 
-  supplemental_includes = GetSupplementalFiles()
-
-  if not RunGN(supplemental_includes):
-    sys.exit(1)
-
-  args.extend(
-      ['-I' + i for i in additional_include_files(supplemental_includes, args)])
-
   # There shouldn't be a circular dependency relationship between .gyp files,
   # but in Chromium's .gyp files, on non-Mac platforms, circular relationships
   # currently exist.  The check for circular dependencies is currently
   # bypassed on other platforms, but is left enabled on the Mac, where a
   # violation of the rule causes Xcode to misbehave badly.
   # TODO(mark): Find and kill remaining circular dependencies, and remove this
   # option.  http://crbug.com/35878.
   # TODO(tc): Fix circular dependencies in ChromiumOS then add linux2 to the
   # list.
   if sys.platform not in ('darwin',):
@@ skipping 46 matching lines @@
         for s in ('sys64', 'sys32'))
     os.environ['PATH'] = runtime_path + os.environ['PATH']
     print('Using automatic toolchain in %s.' % toolchain)
 
   # If CHROMIUM_GYP_SYNTAX_CHECK is set to 1, it will invoke gyp with --check
   # to enfore syntax checking.
   syntax_check = os.environ.get('CHROMIUM_GYP_SYNTAX_CHECK')
   if syntax_check and int(syntax_check):
     args.append('--check')
 
+  supplemental_includes = GetSupplementalFiles()
+  if not RunGN(supplemental_includes):
+    sys.exit(1)
+  args.extend(
+      ['-I' + i for i in additional_include_files(supplemental_includes, args)])
+
   print 'Updating projects from gyp files...'
   sys.stdout.flush()
 
   # Off we go...
   sys.exit(gyp.main(args))