This adds a V8-side script to list the files contained in an official archive.

This'll accompany the infra-side archive recipe:
https://chromium-review.googlesource.com/c/544298/

Keeping this script on the V8-side will make it easy to change the
archived build product.

NOTRY=true

Bug: v8:5918
Change-Id: I9fcb2eae183a26e7ce11c839d95a583a049cbe75
Reviewed-on: https://chromium-review.googlesource.com/544877
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Daniel Vogelheim <vogelheim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46135}