The usual recommendations have been given. Now for more touristic approach what I would like to use if given excuse and time. All those options are mostly written in C:
- QBE [1] - small compiler backend with nice IL
- DynASM [2] - IIUC the laujit's backend, that can and is used by other languages
- uBPF - Userspace eBPF VM. Depending on your DSL the eBPF toolchain could fit your use-case, but this would probably be the biggest excursion. There is some basic assembler in python.