lldb RISC-V support

[kasperk81]

On RISC-V, gdb is not always a suitable option to debug programs, especially for folks who use lldb plugins on other architectures. Without the working lldb, debugging code can be quite challenging.

D62732 is in review for over three years and there is no indication whether it is moving forward or abandoned. I realize that it is a matter of prioritization, but if someone else in the community can help with testing on riscv64/32, please do so. Or better yet, if you are familiar with lldb code-base, resubmit the patch.

[llvmbot]

@llvm/issue-subscribers-backend-risc-v

[llvmbot]

@llvm/issue-subscribers-lldb