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

fletch.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': 'fletch-vm',
       'type': 'none',
       'dependencies': [
         'src/vm/vm.gyp:fletch-vm',
       ],
     },
     {
       'target_name': 'c_test_library',
       'type': 'none',
       'dependencies': [
         'src/vm/vm.gyp:ffi_test_library',
       ],
     },
     {
+      'target_name': 'mdns_extension_lib',
+      'type': 'none',
+      'dependencies': [
+        'src/pkg/mdns/mdns.gyp:mdns_extension_lib',
+      ],
+    },
+    {
       'target_name': 'natives_json',
       'type': 'none',
       'toolsets': ['host'],
       'dependencies': [
         'src/shared/shared.gyp:natives_json',
       ],
     },
     {
       'target_name': 'flashtool',
       'type': 'none',
@@ skipping 30 matching lines @@
         {
           'destination': '<(PRODUCT_DIR)',
           'files': [
             'third_party/bin/<(OS)/dart<(EXECUTABLE_SUFFIX)',
           ],
         },
       ],
     },
   ],
 }