[llvm] [AArch64] support `.arch_extension dit` (PR #169999)

[David Spickett via llvm-commits]

DavidSpickett wrote:

> Please make sure the commit message reflects the extended change.

I'm reading this change for the first time and I don't believe that this has been done, or you updated the literal commit message but not the PR description.

The way LLVM merges PRs is the commit message of the final merged commit is taken from the PR description. Which is not that obvious but it is what it is.

So please update the PR description (https://github.com/llvm/llvm-project/pull/169999#issue-3676805104) and PR title and probably we can merge this today given the approvals that it has.

https://github.com/llvm/llvm-project/pull/169999