Add pnacl shims to the chrome build.

ppapi/native_client/src/untrusted/pnacl_irt_shim/pnacl_irt_shim.gyp

+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+  'includes': [
+    '../../../../../native_client/build/untrusted.gypi',
+  ],
+  'targets': [
+    {
+      'target_name': 'pnacl_irt_shim',
+      'type': 'none',
+      'variables': {
+        'nlib_target': 'pnacl_irt_shim.a',
+        'out_newlib64': '<(PRODUCT_DIR)/libpnacl_irt_shim.a',
+        'build_glibc': 0,
+        'build_newlib': 1,
+        'enable_x86_32': 0,
+        'enable_arm': 0,
+        'sources': [
+          'pnacl_shim.c',
+          'shim_entry.c',
+          'shim_ppapi.c',
+        ],
+      },
+      'dependencies': [
+        '<(DEPTH)/native_client/tools.gyp:prep_toolchain',
+      ],
+    },
+  ],
+}