Make gyp target_arch setting native to chromium/config.py

scripts/slave/recipes/ozone_ecs.expected/basic.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "config",
       "--spec",
       "cache_dir = None\nsolutions = [{'custom_deps': {'src/third_party/WebKit/LayoutTests': None, 'src/webkit/data/layout_tests/LayoutTests': None}, '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', 'managed': True, 'name': 'src', 'url': 'svn://svn-mirror.golo.chromium.org/chrome/trunk/src'}]"
     ],
@@ skipping 58 matching lines @@
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
     "env": {
-      "GYP_DEFINES": "component=static_library embedded=1",
+      "GYP_DEFINES": "component=static_library embedded=1 target_arch=x64",
       "GYP_GENERATORS": "ninja"
     },
     "name": "gclient runhooks"
   },
   {
     "abort_on_failure": true,
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/compile.py",
@@ skipping 461 matching lines @@
       "--no-xvfb",
       "--factory-properties",
       "{\"recipe\": \"ozone_ecs\"}",
       "--build-properties",
       "{\"recipe\": \"ozone_ecs\"}",
       "content_browsertests"
     ],
     "name": "experimentally run content_browsertests"
   }
 ]