Reland "[clang] Make update.py verify that the expected and real versions match"

This is a reland of commit dc9652a8
It includes a fix to package.py to not use --print-version.

Original change's description:
> [clang] Make update.py verify that the expected and real versions match
>
> To fix problems when building with a new version of update.py without
> having run 'gclient sync', which could e.g. lead to PCH files built with
> the wrong clang version being left in the tree (see bug).
>
> Bug: 608105
> Change-Id: Ia5b70506be3f6a89d17742b6b2e0bf3271585d31
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3847019


> Commit-Queue: Hans Wennborg <hans@chromium.org>
> Reviewed-by: Nico Weber <thakis@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1038229}

Bug: 608105
Change-Id: Ia65e4e9350a3048298b06d47968eabc641609eb8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3854616


Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1039192}