Remove PPAPI gyp files.

ppapi/native_client/src/untrusted/irt_stub/irt_stub.gyp

-# Copyright (c) 2011 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': [
-    '../../../../../build/common_untrusted.gypi',
-  ],
-  'targets' : [
-    {
-      'target_name': 'ppapi_stub_lib',
-      'type': 'none',
-      'variables': {
-        'nlib_target': 'libppapi_stub.a',
-        'build_glibc': 1,
-        'build_newlib': 1,
-        'build_pnacl_newlib': 1,
-      },
-      # Always compile libppapi_stub with -fPIC so that -lppapi can be linked
-      # into shared libraries (libppapi.so is a linker script that pulls in
-      # ppapi_stub).
-      'compile_flags': [ '-fPIC' ],
-      'include_dirs': [
-        '../../../..',
-      ],
-      'sources': [
-        'plugin_main_irt.c',
-        'ppapi_plugin_main.c',
-        'ppapi_plugin_start.c',
-        'thread_creator.c'
-      ],
-    },
-  ],
-}