[clang] [lld] [llvm] [MTE] Improve memtag support for non-Android AArch64 targets (PR #183275)

[Elia Geretto via cfe-commits]

EliaGeretto wrote:

> > > > Thanks for putting up llvm/clang/lld together to make the full picture clear, but when you are ready for a real review, ensure lld changes are extracted to a separate patch.
> > > 
> > > 
> > > @MaskRay I have three commits, one for lld, one for the clang Driver and one for llvm CodeGen. Is this ok or do you want me to break things up more?
> > 
> > 
> > Unfortunately this repo is configured to only allow ["Squash and merge"](https://maskray.me/blog/2023-09-09-reflections-on-llvm-switch-to-github-pull-requests#commit-message). The merged patch gets a single commit. In this case we do want separate commits, which can only be achieved with multiple PRs.
> 
> Which will make the new approach of using the same flags for Android and non-Android a bit harder, because now between the commits LLD and the driver will be out of sync

Ah, right, that's because we would break backwards compatibility in `lld` with my change. So maybe the best solution is to have two PRs. One that groups lld and clang driver changes together and one for memtag-globals. That will make the change atomic enough not to break anything.

https://github.com/llvm/llvm-project/pull/183275