[clang] [Clang][AArch64] Command-line options for A-profile's Sign Return Address Hardening (PR #176171)

[Anatoly Trosinenko via cfe-commits]

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atrosinenko wrote:

Maybe it also worth testing what happens when no `-mharden-pac-ret=...` is passed to the driver at all? Something like `ABSENT-RA-HARDEN-NOT: -mharden-pac-ret` or `ABSENT-RA-HARDEN: -mharden-pac-ret=none`, not sure what actually happens.

https://github.com/llvm/llvm-project/pull/176171