/**
 * Creates the output directory, translating the two ways a path can already be
 * taken by something that is not a directory into an actionable message.
 *
 * `mkdir --out-dir` on an existing *file* fails with a raw
 * `EEXIST: file already exists, mkdir '/abs/path'` (and `ENOTDIR` when a file sits
 * midway through the path), which reads like an mjst bug rather than "you pointed
 * --out-dir at a file".
 */
export declare const ensureOutputDir: (dir: string) => Promise<void>;