old_contents: {
    'targets': [
      {
        'target_name': 'addon',
        'sources': [ 'src/addon.cc' ],
        'cflags': [ '-stdlib=libc++', '-std=c++11' ],
        'ldflags': [ '-std=c++11' ],
        'xcode_settings': {
          'OTHER_CPLUSPLUSFLAGS': [ '-mmacosx-version-min=10.7', '-stdlib=libc++', '-std=c++11' ],
          'OTHER_LDFLAGS': [ '-std=c++11' ],
        },
      }
    ]
  }
  
new_contents: {
    'targets': [
      {
        'target_name': 'addon',
        'sources': [ 'src/addon.cc' ],
        'cflags': [ '-std=c++11' ],
        'ldflags': [ '-std=c++11' ],
        'conditions': [
          ['OS=="mac"',
            {
              'cflags': [ '-stdlib=libc++' ],
              'xcode_settings': {
                'OTHER_CPLUSPLUSFLAGS': [ '-mmacosx-version-min=10.7', '-stdlib=libc++', '-std=c++11' ],
                'OTHER_LDFLAGS': [ '-std=c++11' ],
              }
            }
          ],
        ]
      }
    ]
  }
  
subject: move -stdlib directive to mac conditional