canDeleteOutputPath(outputPath) {
    let rootPathParents = [this.project.root];
    let dir = path.dirname(this.project.root);
    rootPathParents.push(dir);
    while (dir !== path.dirname(dir)) {
      dir = path.dirname(dir);
      rootPathParents.push(dir);
    }
    return rootPathParents.indexOf(outputPath) === -1;
  }
Determine whether the output path is safe to delete. If the outputPath
    appears anywhere in the parents of the project root, the build would
    delete the project directory. In this case return `false`, otherwise
    return `true`.

    @private
    @method canDeleteOutputPath
    @param {String} outputPath
    @return {Boolean}