[llvm] [ARM] Emit an error when the hard-float ABI is enabled but can't be used (PR #111334)

[Peter Smith via llvm-commits]

smithp35 wrote:

I'm hoping to take a look, but it may be some time as I've forgotten most of the details and have built up quite a bit of backlog (including internal stuff). Best bet is to keep pinging at the usual once per week frequency so I don't forget about it. 

https://github.com/llvm/llvm-project/pull/111334