[llvm] [emacs] Add noext as an attribute in llvm-mode.el (PR #121444)

[via llvm-commits]

goldsteinn wrote:

> Thanks.
> 
> I tried to merge it here, but I got a mail:
> 
> "LLVM Premerge Checks: All jobs have failed" https://github.com/llvm/llvm-project/actions/runs/12585196983 @goldsteinn

Don't worry about that. Change is in and I don't see it get reverted.

https://github.com/llvm/llvm-project/pull/121444