/**
 * Builds an abort error, using the AbortSignal's reason if available.
 *
 * @param abortSignal - Optional AbortSignal that may contain a reason.
 * @returns A new Error with name "AbortError". If the signal has a reason that's
 *          already an Error, the reason is set as `cause`. Otherwise creates a
 *          new Error with the reason as the message, or "Request aborted" if no
 *          reason.
 */
export declare function buildAbortError(abortSignal?: unknown): Error;