Disable LTO on Mac when building AVX2 target.

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 106 matching lines @@
       'cflags': [ '-mavx2', ],
       'xcode_settings': { 'OTHER_CFLAGS': [ '-mavx2' ] },
       'msvs_settings': {
         'VCCLCompilerTool': {
           'EnableEnhancedInstructionSet': '5', # /arch:AVX2
         },
       },
       # TODO(pcc): Remove this once we properly support subtarget specific
       # code generation in LLVM (http://llvm.org/PR19416).
       'cflags!': [ '-flto', '-fsanitize=cfi-vptr', ],
+      'target_conditions': [
+        ['_toolset=="target"', {
+          'xcode_settings': {
+            'LLVM_LTO': 'NO',
+          },
+        }],
+      ],
     },
   ],
 }