Add a stub nacl_win64 target when disable_nacl=1 so that

chrome/nacl.gypi

 # Copyright (c) 2011 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.
 
 {
   'target_defaults': {
     'variables': {
       'nacl_target': 0,
     },
     'target_conditions': [
@@ skipping 340 matching lines @@
         }],
       ],
     }, {  # else (disable_nacl==1)
       'targets': [
         {
           'target_name': 'nacl',
           'type': 'none',
           'sources': [],
         },
       ],
+      'conditions': [
+        ['OS=="win"', {
+          'targets': [
+            {
+              'target_name': 'nacl_win64',
+              'type': 'none',
+              'sources': [],
+            },
+          ],
+        }],
+      ],
     }],
   ],
 }