[clang] [llvm] [AArch64][clang][llvm] Allow +hcx to be specified as optional for Armv8.6 (PR #208019)

[via cfe-commits]

Lukacma wrote:

> I can do, but it has large ripple effects

I would personally still go for it as the current message is misleading, but I see your point as well. @CarolineConcatto  what do you think ? As for wording, I am not too particular about it as long as it captures that it has no effect and is there for legacy reasons. I wonder about whether other targets already have such retired feature flags and we could maybe just copy how they did it ?

https://github.com/llvm/llvm-project/pull/208019