I wonder if there will ever be a de facto API wrapper for LLVM. As it is, I'm aware of smaller efforts here and there, but other than SPIR-V [1] I'm not sure any are big enough to have long-term survivability potential. And even with SPIR-V I'm not sure if the momentum is really there or not.
[1]: https://www.khronos.org/registry/spir-v/specs/1.0/SPIRV.pdf
Yea, it's annoying. For PostgreSQL I've decided to focus on the C API wherever possible exactly out of that reason. A bit more painful to write, but not even remotely as quickly moving. Obviously there's parts where that's not possible - but even there I've decided to localize that as much as possible.