[clang] [PAC][Driver] Add `-faarch64-jump-table-hardening` flag (PR #113149)

[Daniil Kovalev via cfe-commits]

kovdan01 wrote:

> LGTM
> 
> I expect some discussion in the description / commit message why AArch64JumpTableHardening is placed together with other `PointerAuth*` options.

@MaskRay Thanks for feedback, please let me know if the following description addresses your comment:

> The flag is placed together with pointer authentication flags since they
> serve the same security purpose of protecting against attacks on control
> flow. The flag is not ABI-affecting and might be enabled separately if
> needed, but it's also intended to be enabled as part of pauth-enabled
> environments (e.g. pauthtest).
>
> See also codegen implementation #97666.

https://github.com/llvm/llvm-project/pull/113149