Saw in #4191 that we were going to update make-dir. Was wondering what we used it for and saw we only use it in one file (build/shared/create-file.js which in turn is used in our rule generation script to create all the files) and that we could just replace it with fs.mkdir with the recursive: true flag. Also simplified the file to use fs.promises instead of utils.promisify (all available since node 10.1).