third_party: Add support for building libffi for ARM.

third_party/libffi/libffi.gyp

 # Copyright 2015 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.
 
 {
   'targets': [
     {
       'target_name': 'libffi',
       'type': 'static_library',
       'sources': [
@@ skipping 17 matching lines @@
           'include_dirs': [
             'include/x86_64-unknown-linux-gnu',
             'include/x86_64-unknown-linux-gnu/include',
           ],
           'direct_dependent_settings': {
             'include_dirs': [
               'include/x86_64-unknown-linux-gnu/include',
             ],
           },
         }],
+        ['target_arch=="arm"', {
+          'sources': [
+            'src/src/arm/ffi.c',
+            'src/src/arm/sysv.S',
+          ],
+          'include_dirs': [
+            'include/arm-unknown-linux-gnu',
+            'include/arm-unknown-linux-gnu/include',
+          ],
+          'direct_dependent_settings': {
+            'include_dirs': [
+              'include/arm-unknown-linux-gnu/include',
+            ],
+          },
+        }],
       ],
     },
   ],
 }