Make NaCl IPC-based PPAPI proxy build on ARM.

build/common_untrusted.gypi

+# 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.
+
+# This GYP file should be included for every target in Chromium that is built
+# using the NaCl toolchain.
+{
+  'includes': [
+    '../native_client/build/untrusted.gypi',
+  ],
+  'target_defaults': {
+    'variables': {
+      'conditions': [
+        ['target_arch=="arm"', {
+          'clang': 1,
+          'defines': [
+            # Needed by build/build_config.h processor architecture detection.
+            '__ARMEL__',
+            # Needed by base/third_party/nspr/prtime.cc.
+            '__arm__',
+            # Disable ValGrind. The assembly code it generates causes the build
+            # to fail.
+            'NVALGRIND',
+          ],
+        }],
+      ],
+    },
+  },
+}