code: function checkCompile (dir) {
    return function  (mode, callback) {
      var exercise = this
  
      if (!exercise.passed)
        return callback(null, true) // shortcut if we've already had a failure
  
      gyp.rebuild(dir, function (err) {
        if (err) {
          exercise.emit('fail', err.message)
          return callback(null, false)
        }
  
        callback(null, true)
      })
    }
  }
docs: run a `node-gyp rebuild` on their unmolested code in our copy