We have a locally-maintained bot that periodically builds a known-good version of CrOS with llvm ToT, and runs VM smoke tests to verify that everything seems to work for amd64-generic.

Getting this all to run nicely on CrOS infra is a goal once we see how much value this actually provides. :)

We'd like to use this bot to start detecting warnings that appear in our builds.

How we plan to go about this is detailed here: https://docs.google.com/document/d/1Yet7_JIdVrnfHWpE0aeMVJxh6jXKFvjKwyLl2za0HEg/edit?usp=sharing

Steps:
- Upstream local patches that make -Wno-error possible
- Make the wrapper do what's detailed in the script
- Monitor the local bot to see how much noise it makes
- Profit in the form of not having to trudge through lots of new warnings on every llvm-next roll (or at least knowing what all of those warnings will be ahead of time)