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

[Daniil Kovalev via cfe-commits]

kovdan01 wrote:

> Given the complexity of the feature and lack of upstream runtime linker (rtld) support, it might be wise to delay exposing it through driver options until it's more mature. What do you think?

@MaskRay I suppose that if exposing this to driver options is considered undesirable at the moment, we can just add cc1 option. A cc1 option is actually needed to construct pauth-enabled environments - currently, it is done by adding a predefined set of `-fptrauth-*` flags, see `handlePAuthABI` function.

If we only add cc1 flag and postpone adding driver flag, would it be OK?

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