GN: Fix skia build on mac, use -msse4.1 everywhere

skia/BUILD.gn

Index: skia/BUILD.gn
diff --git a/skia/BUILD.gn b/skia/BUILD.gn
index 55266f471ec995c31e666030939171bc4c55861b..01d1d37a83879d9002e8985ae97939be752cd201 100644
--- a/skia/BUILD.gn
+++ b/skia/BUILD.gn
@@ -136,6 +136,10 @@ config("skia_config") {
       "USE_CHROMIUM_SKIA",
     ]
   }
+
+  if (is_mac) {
+    defines += [ "SK_BUILD_FOR_MAC" ]
+  }
 }
 
 # Internal-facing config for Skia library code.
@@ -559,8 +563,10 @@ source_set("skia_opts") {
       sources += [ "//third_party/skia/src/opts/SkBlitRow_opts_SSE4_x64_asm.S" ]
     }
 
-    if (is_linux || is_mac) {
+    if (is_linux) {
       cflags += [ "-msse4" ]
+    } else if (is_mac) {
+      cflags += [ "-msse4.1" ]

[Nico, 2014/07/08 17:20:52]

Is this actually needed? This currently uses msse4.1 in gyp probably because
there's GCC_ENABLE_SSE41_EXTENSIONS but no GCC_ENABLE_SSE4_EXTENSIONS in Xcode
(maybe there's no chip that supports sse4 but no sse4.1 in apple computers?) In
gyp, it makes sense to keep this separate, but in gn it might not.

     }
   } else if (cpu_arch == "arm") {
     sources = [