Make gyp target_arch setting native to chromium/config.py

scripts/slave/recipe_modules/gclient/config.expected/using_mirror-True-git_mode-True-cache_dir-True.json

Index: scripts/slave/recipe_modules/gclient/config.expected/using_mirror-True-git_mode-True-cache_dir-True.json
diff --git a/scripts/slave/recipe_modules/gclient/config.expected/using_mirror-True-git_mode-True-cache_dir-True.json b/scripts/slave/recipe_modules/gclient/config.expected/using_mirror-True-git_mode-True-cache_dir-True.json
index c7237c3a41a44c3d4ecdfbcc7ef1ef2cbcb487b5..759324199a2d6708c5a1bd9a2e7736dc7826d94b 100644
--- a/scripts/slave/recipe_modules/gclient/config.expected/using_mirror-True-git_mode-True-cache_dir-True.json
+++ b/scripts/slave/recipe_modules/gclient/config.expected/using_mirror-True-git_mode-True-cache_dir-True.json
@@ -166,6 +166,28 @@
       }
     ]
   }, 
+  "libvpx": {
+    "cache_dir": "CACHE_DIR", 
+    "solutions": [
+      {
+        "custom_deps": {
+          "src/third_party/WebKit/LayoutTests": null, 
+          "src/third_party/libvpx/source2/libvpx": "https://chromium.googlesource.com/webm/libvpx.git", 
+          "src/webkit/data/layout_tests/LayoutTests": null
+        }, 
+        "custom_vars": {
+          "googlecode_url": "svn://svn-mirror.golo.chromium.org/%s", 
+          "nacl_trunk": "svn://svn-mirror.golo.chromium.org/native_client/trunk", 
+          "sourceforge_url": "svn://svn-mirror.golo.chromium.org/%(repo)s", 
+          "webkit_trunk": "svn://svn-mirror.golo.chromium.org/blink/trunk"
+        }, 
+        "deps_file": ".DEPS.git", 
+        "managed": true, 
+        "name": "src", 
+        "url": "https://chromium.googlesource.com/chromium/src.git"
+      }
+    ]
+  }, 
   "nacl": "nacl only supports svn", 
   "oilpan": "Oilpan requires SVN for now", 
   "oilpan_internal": "config \"oilpan_internal\" includes \"oilpan\", but [Oilpan requires SVN for now]",