Add support for hosting ceph-boost's RISCV deb package

When running `install-deps.sh` on a Debian system, Ceph relies on ceph-boost. However, ceph-boost currently does not support the RISCV architecture, preventing the `install-deps.sh` from executing.

I packaged and tested ceph-boost on RISCV using a GitHub action [link](https://github.com/ffgan/ceph-boost-riscv/actions/runs/16500969083/job/46659144626). The packaged deb also works properly and can be run through `install-deps.sh`. Therefore, we are considering adding support for hosting ceph-boost's RISCV deb on chacra.ceph.com.

You can see all the build, test, and packaging scripts in the yml file of my github action, [link](https://github.com/ffgan/ceph-boost-riscv/blob/master/.github/workflows/CI.yaml)

Feel free to contact me, I'd be happy to provide more information