This reverts commit 0aa05cca9db25a9fa8d18f77bf6b2452bc608ead.

Reason for revert:
This broke arm64-builder-rel and some other builders, see bug.

Original change's description:
> Roll clang n333938-3a6da112-1 : n340158-efb130fc-2.
> 
> Ran `tools/clang/scripts/upload_revision.py efb130fc93059bdf02d3a83950ddabc5d119f9de`.
> 
> This increases the clang version from 10 to 11.
> 
> It also disables the use of vector instructions in zlib to work around
> new false positives in msan (see crbug.com/1045291).
> 
> Bug: 1030664
> Change-Id: I5417d3063f0d67a61cdf31141b05a51a56e84482
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2014904


> Reviewed-by: Nico Weber <thakis@chromium.org>
> Commit-Queue: Hans Wennborg <hans@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#735080}

TBR=thakis@chromium.org,hans@chromium.org

Change-Id: I48754484c26ebf6b1f0b4a47c82fe3c74ee39837
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1030664,1045592
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2020785


Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#735124}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: ec2aab7d123590cfb332ba56d7faee2e1ff4a779