[LLVMdev] Contributing the Apple ARM64 compiler backend

[Tim Northover]

Hi all,

>> Tim has volunteered to commit the initial changes tomorrow.
>
> Sounds great, thank you Tim!

Well, the key parts are committed now and I think the bots are back to
whatever state they were in before with the last Msan fix by Alexey
this morning.

This is just the start, of course, not the end of the integration
process. If anyone spots any suspect code or has other problems, we'd
still love to hear about it.

Cheers.

Tim.