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

[Daniil Kovalev via llvm-commits]

kovdan01 wrote:

> Does this need a clang command line option at this point? Would it be possible to live with a {{-mllvm}} option to turn on signed GOT? I would expect signed GOT (or not) would be part of a higher-level signing schema and not toggled at a low-level via clang.
> 
> I know that there are existing command-line options for other signing schema affecting options, but I'm not sure if we want to add more to them.

@smithp35 Theoretically, we can use `-mllvm` and it was actually used for some time during downstream implementation and testing. I agree that a ton of `-fptrauth-*` flags is pretty annoying (and there was already a discussion in this PR which I've transformed into an issue #97320).

However, as you correctly mentioned, we already have other similar flags and they are also not intended to be used manually and, instead, should be a part of high-level signing schema. As for me, it's better to keep things consistent at each moment - if we use clang driver flags, we use them everywhere, and if we want to refactor that and move to `-mllvm`, we want to do that for all the ptrauth flags as well.

So, if it's not a very huge concern right now, I'd prefer to introduce `-fptrauth-elf-got` flag in this PR and, after further discussion, probably refactor all the flags logic in subsequent PRs (either move to comma-separeted flags as discussed above or use `-mllvm` or, maybe, we'll find other ways to enhance this - it's still needs to be discussed).

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