Remove gyp support from libvpx

third_party/libvpx/libvpx_nacl.gyp

-# Copyright 2013 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.
-{
-  'variables': {
-    'libvpx_source%': 'source/libvpx',
-    'werror': '',
-  },
-  'includes': [
-    '../../native_client/build/untrusted.gypi',
-  ],
-  'targets': [
-    {
-      'target_name': 'libvpx_nacl',
-      'type': 'none',
-      'variables': {
-        'nlib_target': 'libvpx_nacl.a',
-        'build_glibc': 0,
-        'build_newlib': 0,
-        'build_pnacl_newlib': 1,
-      },
-      'include_dirs': [
-        'source/config/nacl',
-        'source/config',
-        '<(libvpx_source)',
-        '<(libvpx_source)/vp8/common',
-        '<(libvpx_source)/vp8/decoder',
-        '<(libvpx_source)/vp8/encoder',
-      ],
-      'includes': ['libvpx_srcs_nacl.gypi', ],
-    },  # end of target 'libvpx_nacl'
-  ],
-}