Migration to ORC JIT for llvmpipe to run on RISC-V

Dear mesa developers,

I am trying to run mesa with llvmpipe on a RISC-V platform, without
success. This is needed in order to get some performance figures for the
RISC-V Graphics SIG.

By default llvmpipe is using MCJIT and crashes on
lp_build_create_jit_compiler_for_module because MCJit does not support
RISC-V.

Seems like MCJIT is deprecated and it is not going to accept new
architectures, so llvmpipe will never run on RISC-V unless ported to ORC
JIT. I see there is already a merge request for migrating llvmpipe from the
deprecated MCJIT to the new ORC JIT:

https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17801

My understanding is that the code is good for merging in a disabled state
(rather than enabled by default). However the merge is gated by the fact
that a meson build option is still missing.

Do the mesa developers need help with this? I could try to add the missing
option myself if that helps, as this task is critical for supporting basic
graphics on RISC-V. Let me know what RISC-V can do to help.

Regards.