spin off some safe parts from AVX2 CL

gyp/opts.gyp

 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 # Gyp file for building opts target.
 {
   # Source lists live in opts.gypi.  This makes it easier to maintain our Chrome GYP/GN setup.
   # (To be honest, I'm not sure why we need to include common.gypi.  I thought it was automatic.)
   'variables': {
     'includes': [ 'common.gypi', 'opts.gypi' ],
@@ skipping 131 matching lines @@
       'type': 'static_library',
       'standalone_static_library': 1,
       'dependencies': [ 'core.gyp:*' ],
       'include_dirs': [
           '../include/private',
           '../src/core',
           '../src/utils',
       ],
       'sources': [ '<@(avx_sources)' ],
       'msvs_settings': { 'VCCLCompilerTool': { 'EnableEnhancedInstructionSet': '3' } },
-      'xcode_settings': { 'OTHER_CFLAGS': [ '-mavx' ] },
+      'xcode_settings': { 'OTHER_CPLUSPLUSFLAGS': [ '-mavx' ] },
       'conditions': [
         [ 'not skia_android_framework', { 'cflags': [ '-mavx' ] }],
       ],
     },
     {
       'target_name': 'opts_avx2',
       'product_name': 'skia_opts_avx2',
       'type': 'static_library',
       'standalone_static_library': 1,
       'dependencies': [ 'core.gyp:*' ],
       'include_dirs': [
           '../include/private',
           '../src/core',
           '../src/utils',
       ],
       'sources': [ '<@(avx2_sources)' ],
       'msvs_settings': { 'VCCLCompilerTool': { 'EnableEnhancedInstructionSet': '5' } },
-      'xcode_settings': { 'OTHER_CFLAGS': [ '-mavx2' ] },
+      'xcode_settings': { 'OTHER_CPLUSPLUSFLAGS': [ '-mavx2' ] },
       'conditions': [
         [ 'not skia_android_framework', { 'cflags': [ '-mavx2' ] }],
       ],
     },
     {
       'target_name': 'opts_neon',
       'product_name': 'skia_opts_neon',
       'type': 'static_library',
       'standalone_static_library': 1,
       'dependencies': [
@@ skipping 21 matching lines @@
           ],
         }],
       ],
       'ldflags': [
         '-march=armv7-a',
         '-Wl,--fix-cortex-a8',
       ],
     },
   ],
 }