Add unittest for 'AR' in 'make_global_settings'

test/make_global_settings/ar/make_global_settings_ar.gyp

+# Copyright (c) 2014 Google Inc. All rights reserved.
+# Use of this source code is governed by a BSD-style licence that can be
+# found in the LICENSE file.
+
+{
+  'variables': {
+    'custom_ar_target%': '',
+    'custom_ar_host%': '',
+  },
+  'conditions': [
+    ['"<(custom_ar_target)"!=""', {
+      'make_global_settings': [
+        ['AR', '<(custom_ar_target)'],
+      ],
+    }],
+    ['"<(custom_ar_host)"!=""', {
+      'make_global_settings': [
+        ['AR.host', '<(custom_ar_host)'],
+      ],
+    }],
+  ],
+  'targets': [
+    {
+      'target_name': 'make_global_settings_ar_test',
+      'type': 'static_library',
+      'sources': [ 'foo.c' ],
+    },
+  ],
+}