[clang] [Clang] Allow diagnostics starting with Arm (PR #98091)

[Jon Roelofs via cfe-commits]

jroelofs wrote:

This one looks fairly benign, and while I agree that it is good to upstream things wherever possible, my slight objection rests mostly on two principles:

* In general the community doesn't take behavior-changing patches purely on the basis of eliminating merge conflicts for code that is out of tree. Things that go upstream need to have a justification that is relevant to upstream.
* Changes that land need to come with tests that exercise them.

FWIW, this particular change looks unlikely to be a source of merge conflicts, as it adds only a single line to a table that is unlikely to be touched very often. I think you'll be okay if this isn't upstream, but I won't complain too loudly if you feel the need to land this anyway.

https://github.com/llvm/llvm-project/pull/98091