[clang] [llvm] [TargetLibraryInfo] Add libmvec support for risc-v (PR #119844)

[Mark Goncharov via llvm-commits]

https://github.com/mga-sc requested changes to this pull request.

Finally, libmvec is still not ported to RISC-V (today check glibc ToT with `--enable-mathvec`). I think we should wait for this and also wait for commit to [riscv-elf-psabi-doc](https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/455). Probably, implementation will differ from the proposals.

https://github.com/llvm/llvm-project/pull/119844