Derive default for ar_host from ar.

test/make_global_settings/ar/gyptest-make_global_settings_ar.py

 #!/usr/bin/env python
 
 # Copyright (c) 2014 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 Verifies 'AR' in make_global_settings.
 """
 
@@ skipping 38 matching lines @@
     test.fail_test()
 
 
 def verify_ar_host(test, ar=None, rel_path=False):
   if rel_path:
     ar_expected = resolve_path(test, ar)
   else:
     ar_expected = ar
   # Resolve default values
   if ar_expected is None:
-    ar_expected = 'ar'
+    if sys.platform == 'win32':
+      ar_expected = 'lib.exe'
+    else:
+      ar_expected = 'ar'
   if test.format == 'make':
     test.must_contain('Makefile', 'AR.host ?= %s' % ar_expected)
   elif test.format in ['ninja', 'xcode-ninja']:
     test.must_contain('out/Default/build.ninja', 'ar_host = %s' % ar_expected)
   else:
     test.fail_test()
 
 
 test_format = ['ninja']
 if sys.platform in ('linux2', 'darwin'):
@@ skipping 44 matching lines @@
 
 # Test 'AR' in 'make_global_settings' with $AR_host environment variable.
 with TestGyp.LocalEnv({'AR_host': 'my_ar_host3'}):
   test.run_gyp('make_global_settings_ar.gyp',
                '-Dcustom_ar_target=my_ar_target3')
 verify_ar_target(test, ar='my_ar_target3', rel_path=True)
 verify_ar_host(test, ar='my_ar_host3', rel_path=False)
 
 
 test.pass_test()