[clang] [PAC][clang][Driver] Add signed GOT flag (PR #96160)

[Ahmed Bougacha via cfe-commits]

ahmedbougacha wrote:

>> Do we want a lot of -fptrauth-xxx instead of -fptrauth-something=xxx,yyy,zzz?
>
> I would lean towards a single flag.

Comma-separated flags generally seem less user-friendly (for, e.g., grepping, modifying, reading).  To some extent we can mitigate that with the obvious cleverness (e.g., negatives, repetition), at the cost of a lot more driver logic, and even that would only go so far.

Is there a compelling argument for them?

> However, I do not know how this would affect Apple downstream and what are preferences there.

Yeah, we do already support the long spellings, but we can change these here if we have consensus, and it should be doable to support the long spellings on top of these.

https://github.com/llvm/llvm-project/pull/96160