Derive default for ar_host from ar.

test/win/lib-crosscompile/use_host_ar.gyp

Index: test/win/lib-crosscompile/use_host_ar.gyp
diff --git a/test/win/lib-flags/ltcg.gyp b/test/win/lib-crosscompile/use_host_ar.gyp
similarity index 52%
copy from test/win/lib-flags/ltcg.gyp
copy to test/win/lib-crosscompile/use_host_ar.gyp
index c183107730ad2c96dd7988f0265f0f9091842ecb..5587da95e1c523ade664b4f98541d86477e32120 100644
--- a/test/win/lib-flags/ltcg.gyp
+++ b/test/win/lib-crosscompile/use_host_ar.gyp
@@ -1,21 +1,17 @@
-# Copyright (c) 2012 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.
-
-{
- 'targets': [
-    {
-      'target_name': 'lib_answer',
-      'type': 'static_library',
-      'msvs_settings': {
-        'VCCLCompilerTool': {
-          'WholeProgramOptimization': 'true',  # /GL
-        },
-        'VCLibrarianTool': {
-          'LinkTimeCodeGeneration': 'true',    # /LTCG
-        },
-      },
-      'sources': ['answer.cc'],
-    },
-  ]
-}
+# Copyright (c) 2015 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.
+
+{
+ 'targets': [
+    {
+      'target_name': 'lib_answer',
+      'type': 'static_library',
+      'toolsets': ['host'],
+      'msvs_settings': {
+        'msvs_cygwin_shell': 0,
+      },
+      'sources': ['answer.cc'],
+    },
+  ]
+}