[clang] [clang] Improve diagnostics for constraints of inline asm (NFC) (PR #96363)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

What exactly does it mean for a constraint to conflict with a feature?  The only thing I can think of is if it somehow involves a register class that doesn't exist on the target with the current set of target features.  I guess we could try to diagnose that, but I'm not sure it's worth duplicating that code.

https://github.com/llvm/llvm-project/pull/96363