Revert "Extend the mDNS package with a native extension used on Mac OS"

src/pkg/mdns/mdns.gyp

-# Copyright (c) 2015, the Fletch project authors. Please see the AUTHORS file
-# for details. All rights reserved. Use of this source code is governed by a
-# BSD-style license that can be found in the LICENSE.md file.
-
-{
-  'targets': [
-    {
-      'target_name': 'mdns_extension_lib',
-      'type': 'shared_library',
-      'include_dirs': [
-        '../../../third_party/dart/runtime',
-      ],
-      'cflags!': [
-        '-Wnon-virtual-dtor',
-        '-Woverloaded-virtual',
-        '-fno-rtti',
-        '-fvisibility-inlines-hidden',
-        '-Wno-conversion-null',
-      ],
-      'sources': [
-        'mdns_extension.cc',
-        'mdns_extension_linux.cc',
-        'mdns_extension_macos.cc',
-      ],
-      'defines': [
-        # The only effect of DART_SHARED_LIB is to export the Dart API.
-        'DART_SHARED_LIB',
-      ],
-      'conditions': [
-        ['OS=="mac"', {
-          'xcode_settings': {
-            'OTHER_LDFLAGS': [ '-undefined', 'dynamic_lookup' ],
-          },
-        }],
-        ['OS=="linux"', {
-          'cflags': [
-            '-fPIC',
-          ],
-        }],
-      ],
-    },
-  ],
-}