Keep timestamp in aar.py when file is not changed

This is a reland of
https://chromium-review.googlesource.com/c/chromium/src/+/1127565
I didn't understand filecmp.dircmp.

Changed to use md5_check.CallAndRecordIfStale instead.
Also let ExtractAll create directory even when it is empty.

Bug: 810298, 860251
Change-Id: I0d1e2e385ff1a12981473ef422099f638ca174cf
Reviewed-on: https://chromium-review.googlesource.com/1132818
Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574589}
2 files changed