Make gyp target_arch setting native to chromium/config.py

scripts/slave/recipes/gpu/build_and_upload.expected/win_release.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'}, {'custom_deps': {'src/chrome/test/data/firefox2_profile/searchplugins': None, 'src/chrome/test/data/firefox2_searchplugins': None, 'src/chrome/test/data/firefox3_profile/searchplugins': None, 'src/chrome/test/data/firefox3_searchplugins': None, 'src/chrome/test/data/osdd': None, 'src/chrome/test/data/plugin': None, 'src/chrome/test/data/ssl/certs': None, 'src/data/autodiscovery': None, 'src/data/esctf': None, 'src/data/mach_ports': None, 'src/data/memory_test': None, 'src/data/mozilla_js_tests': None, 'src/data/page_cycler': None, 'src/data/selenium_core': None, 'src/data/tab_switching': None, 'src/tools/grit/grit/test/data': None, 'src/webkit/data/bmp_decoder': None, 'src/webkit/data/ico_decoder': None, 'src/webkit/data/test_shell/plugins': None, 'src/webkit/data/xbm_decoder': None}, 'deps_file': 'DEPS', 'managed': True, 'name': 'src-internal', 'url': 'svn://svn-mirror.golo.chromium.org/chrome-internal/trunk/src-internal'}]"
     ],
@@ skipping 60 matching lines @@
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]\\gclient.py",
       "runhooks"
     ],
     "env": {
-      "GYP_DEFINES": "chromium_win_pch=0 component=static_library fastbuild=1 internal_gles2_conform_tests=1",
+      "GYP_DEFINES": "chromium_win_pch=0 component=static_library fastbuild=1 internal_gles2_conform_tests=1 target_arch=ia32",
       "GYP_GENERATORS": "ninja",
       "GYP_MSVS_VERSION": "2010"
     },
     "name": "gclient runhooks"
   },
   {
     "abort_on_failure": true,
     "cmd": [
       "python",
       "-u",
@@ skipping 25 matching lines @@
       "--build-url",
       "gs://chromium-gpu-archive/chromium.gpu.testing/win builder",
       "--factory-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"branch\": \"TestBranch\", \"build_config\": \"Release\", \"buildername\": \"win builder\", \"buildnumber\": 571, \"mastername\": \"chromium.gpu.testing\", \"project\": \"\", \"recipe\": \"gpu/build_and_upload\", \"repository\": \"svn://svn-mirror.golo.chromium.org/chrome/trunk\", \"revision\": \"204787\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--build-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"branch\": \"TestBranch\", \"build_config\": \"Release\", \"buildername\": \"win builder\", \"buildnumber\": 571, \"mastername\": \"chromium.gpu.testing\", \"project\": \"\", \"recipe\": \"gpu/build_and_upload\", \"repository\": \"svn://svn-mirror.golo.chromium.org/chrome/trunk\", \"revision\": \"204787\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}"
     ],
     "name": "package_build"
   }
 ]