[llvm] [ARM] Add test for thumb2-reduce-size NFC (PR #112333)

[via llvm-commits]

VladiKrapp-Arm wrote:

> I see that the pull request has a merge commit in it. What happens if the pull request is merged? Will the merge commit magically go away or will it now be present in the main commits? If the latter please remove the merge commit.

I fixed it with a rebase, there's no merge commit now. 


https://github.com/llvm/llvm-project/pull/112333