[lld] [lld] Add infrastructure for handling RISCV vendor-specific relocations. (PR #159987)

[Jessica Clarke via llvm-commits]

jrtc27 wrote:

It sounds like you want a separate method that's only implemented on RISC-V that takes the vendor as an argument, perhaps? This definitely isn't the right interface.

https://github.com/llvm/llvm-project/pull/159987