Enable AVX2 optimizations for libvpx

libvpx_srcs_x86_intrinsics.gypi

Index: libvpx_srcs_x86_intrinsics.gypi
===================================================================
--- libvpx_srcs_x86_intrinsics.gypi	(revision 263116)
+++ libvpx_srcs_x86_intrinsics.gypi	(working copy)
@@ -85,5 +85,34 @@
         }],
       ],
     },
+    {
+      'target_name': 'libvpx_intrinsics_avx2',
+      'type': 'static_library',
+      'include_dirs': [
+        'source/config/<(OS_CATEGORY)/<(target_arch_full)',
+        '<(libvpx_source)',
+      ],
+      'sources': [
+        '<(libvpx_source)/vp9/common/x86/vp9_loopfilter_intrin_avx2.c',
+        '<(libvpx_source)/vp9/common/x86/vp9_subpixel_8t_intrin_avx2.c',
+        '<(libvpx_source)/vp9/encoder/x86/vp9_dct32x32_avx2.c',
+        '<(libvpx_source)/vp9/encoder/x86/vp9_dct_avx2.c',
+        '<(libvpx_source)/vp9/encoder/x86/vp9_sad4d_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',
+      ],
+      'conditions': [
+        ['os_posix==1 and OS!="mac" and OS!="ios"', {
+          'cflags!': [ '-mfpu=vfpv3-d16' ],
+          'cflags': [ '-mavx2', ],
+        }],
+        ['OS=="mac" or OS=="ios"', {
+          'xcode_settings': {
+            'OTHER_CFLAGS': [ '-mavx2', ],
+          },
+        }],
+      ],
+    },
   ],
 }