fix warning on visual C for mips cpu detect

libyuv_test.gyp

 # Copyright 2011 The LibYuv Project Authors. All rights reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS. All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 {
   'variables': {
     'libyuv_disable_jpeg%': 0,
+    'mips_msa%': 0,  # Default to msa off.
   },
   'targets': [
     {
       'target_name': 'libyuv_unittest',
       'type': '<(gtest_target_type)',
       'dependencies': [
         'libyuv.gyp:libyuv',
         'testing/gtest.gyp:gtest',
         'third_party/gflags/gflags.gyp:gflags',
       ],
@@ skipping 170 matching lines @@
       ],
     }],
   ],
 }
 
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