Function asyncFlatten

packages/vite/src/node/utils.ts:1597–1604

(
  arr: T,
)

  : never

export async function asyncFlatten<T extends unknown[]>(
  arr: T,
): Promise<AsyncFlatten<T>> {
  do {
    arr = (await Promise.all(arr)).flat(Infinity) as any
  } while (arr.some((v: any) => v?.then))
  return arr as unknown[] as AsyncFlatten<T>
}

// strip UTF-8 BOM
export function stripBomTag(content: string): string {