GN: make current_cpu work

BUILD.gn

 # Copyright 2016 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 declare_args() {
 }
 
 skia_public_includes = [
   "include/android",
@@ skipping 126 matching lines @@
 
 utils_gypi = exec_script("gn/gypi_to_gn.py",
                          [
                            rebase_path("gyp/utils.gypi"),
                            "--replace=<(skia_include_path)=include",
                            "--replace=<(skia_src_path)=src",
                          ],
                          "scope",
                          [ "gyp/utils.gypi" ])
 
-source_set("opts_ssse3") {
-  configs += skia_library_configs
+is_x86 = current_cpu == "x64" || current_cpu == "x86"
 
-  sources = opts_gypi.ssse3_sources
-  cflags = [ "-mssse3" ]
-}
+if (is_x86) {
+  source_set("opts_sse2") {
+    configs += skia_library_configs
+    sources = opts_gypi.sse2_sources
+    cflags = [ "-msse2" ]
+  }
 
-source_set("opts_sse41") {
-  configs += skia_library_configs
+  source_set("opts_ssse3") {
+    configs += skia_library_configs
+    sources = opts_gypi.ssse3_sources
+    cflags = [ "-mssse3" ]
+  }
 
-  sources = opts_gypi.sse41_sources
-  cflags = [ "-msse4.1" ]
-}
+  source_set("opts_sse41") {
+    configs += skia_library_configs
+    sources = opts_gypi.sse41_sources
+    cflags = [ "-msse4.1" ]
+  }
 
-source_set("opts_sse42") {
-  configs += skia_library_configs
+  source_set("opts_sse42") {
+    configs += skia_library_configs
+    sources = opts_gypi.sse42_sources
+    cflags = [ "-msse4.2" ]
+  }
 
-  sources = opts_gypi.sse42_sources
-  cflags = [ "-msse4.2" ]
-}
-
-source_set("opts_avx") {
-  configs += skia_library_configs
-
-  sources = opts_gypi.avx_sources
-  cflags = [ "-mavx" ]
+  source_set("opts_avx") {
+    configs += skia_library_configs
+    sources = opts_gypi.avx_sources
+    cflags = [ "-mavx" ]
+  }
 }
 
 component("skia") {
   public_configs = [ ":skia_public" ]
   configs += skia_library_configs
 
   deps = [
-    ":opts_avx",
-    ":opts_sse41",
-    ":opts_sse42",
-    ":opts_ssse3",
     "//third_party/expat",
     "//third_party/giflib",
     "//third_party/libjpeg_turbo",
     "//third_party/libpng",
     "//third_party/libwebp",
     "//third_party/sfntly",
     "//third_party/zlib",
   ]
+  if (is_x86) {
+    deps += [
+      ":opts_avx",
+      ":opts_sse2",
+      ":opts_sse41",
+      ":opts_sse42",
+      ":opts_ssse3",
+    ]
+  }
 
   if (!is_win) {
     libs = [ "pthread" ]
   }
 
   sources = []
   sources += core_gypi.sources
   sources += effects_gypi.sources
   sources += gpu_gypi.skgpu_sources
-  sources += opts_gypi.sse2_sources
   sources += pdf_gypi.sources
   sources += utils_gypi.sources
   sources += [
     "src/android/SkBitmapRegionCodec.cpp",
     "src/android/SkBitmapRegionDecoder.cpp",
     "src/codec/SkAndroidCodec.cpp",
     "src/codec/SkBmpCodec.cpp",
     "src/codec/SkBmpMaskCodec.cpp",
     "src/codec/SkBmpRLECodec.cpp",
     "src/codec/SkBmpStandardCodec.cpp",
@@ skipping 379 matching lines @@
       "tools/SkShaper_harfbuzz.cpp",
       "tools/using_skia_and_harfbuzz.cpp",
     ]
     deps = [
       ":skia",
       "//third_party/harfbuzz",
     ]
     testonly = true
   }
 }