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

[Oliver Stannard via cfe-commits]

ostannard wrote:

I agree with the previous comments from @davemgreen and @smithp35, user-facing diagnostics should always be emitted by clang, so that cases like LTO work correctly. If you want to reduce the duplication of the code which works out what ABIs are compatible (which I think would be a good idea), you could probably put that code in `TargetParser`, and use it from clang to decide what error/warning to emit.

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