Use the correct AVX flags for Windows builds

libvpx_srcs_x86_64_intrinsics.gypi

 # This file is generated. Do not edit.
 # Copyright (c) 2014 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': 'libvpx_intrinsics_mmx',
       'type': 'static_library',
@@ skipping 100 matching lines @@
         '<(libvpx_source)/vp9/encoder/x86/vp9_sad4d_intrin_avx2.c',
         '<(libvpx_source)/vp9/encoder/x86/vp9_sad_intrin_avx2.c',
         '<(libvpx_source)/vp9/encoder/x86/vp9_subpel_variance_impl_intrin_avx2.c',
         '<(libvpx_source)/vp9/encoder/x86/vp9_variance_avx2.c',
         '<(libvpx_source)/vp9/encoder/x86/vp9_variance_impl_intrin_avx2.c',
       ],
       'cflags': [ '-mavx2', ],
       'xcode_settings': { 'OTHER_CFLAGS': [ '-mavx2' ] },
       'msvs_settings': {
         'VCCLCompilerTool': {
-          'EnableEnhancedInstructionSet': '3', # /arch:AVX
+          'EnableEnhancedInstructionSet': '5', # /arch:AVX2
         },
       },
     },
   ],
 }