The last clang roll attempt had to be reverted here:
https://bugs.chromium.org/p/chromium/issues/detail?id=871418#c23
Because the official Linux bot went red here:
https://ci.chromium.org/buildbot/chromium.chrome/Google%20Chrome%20Linux%20x64/35385

We don't currently seem to have Linux official build coverage on the tot waterfall.

We could repurpose our existing LTO builder to be the official builder, since right now official builds on Linux use ThinLTO. I think Linux official builds also happen to use CFI today, so we might lose the ability to see if ThinLTO without CFI works. Should we do that, or should we add a new official bot to the waterfall? We could call it "off" or "ofc" in the LUCI UI to match our three letter names.

If we're adding VMs, then I'd also like to have separate bots for the Windows release configuration and the official configuration. The regular release build configuration is probably the most stable build configuration, while the tests never pass in the official build configuration. I'd like to be able to see "green rel, red official, test failures only, OK not our bug, roll clang".

Lastly, maybe this should all happen after the LUCI bot mirroring, which I heard was scheduled for next week.