[host] Add support for R_RISCV_PCREL_LO12_S.

[hvdijk]

Overview

[host] Add support for R_RISCV_PCREL_LO12_S.

Reason for change

Describe how the current behaviour of the project is causing problems for you
or is otherwise unsatisfactory for your use case.

Description of change

R_RISCV_PCREL_LO12_S is like R_RISCV_PCREL_LO12_I, except for S-type instructions rather than I-type instructions, so the handling is mostly identical.

Anything else we should know?

If there's any other relevant information we should know that may help us in
understanding and verifying your patch, please include it here.

Checklist

• Read and follow the project Code of Conduct.
• Make sure the project builds successfully with your changes.
• Run relevant testing locally to avoid regressions.
• Run clang-format-17 on all modified code.