code: function getSharedLinked(pkgs, hash) {
    return pkgs.map((name) => {
      const module = hash[name];
      if (module && module.isLinked) {
        return name;
      }
      return false;
    }).filter(Boolean);
  }
docs: getSharedLinked selects an array of shared and linked packages
  @param  {Array} pkgs   An array of dependencies
  @param  {Object} hash  A hash map of our deps
  @return {Array}        A filtered list of packages