This implements a very elementary Lua script interpreter. It supports running a single command as well as running interactively. It uses editline if available. It's still missing a bunch of stuff though. Some things that I intentionally ingored for now are that I/O isn't properly hooked up (so every print goes to stdout) and the non-editline support which is not handling a bunch of corner cases. The latter is a matter of reusing existing code in the Python interpreter.
Discussion on the mailing list: http://lists.llvm.org/pipermail/lldb-dev/2019-December/015812.html