I pushed the first patch, for LLVM 16, and the build farm told me that
some old LLVM versions don't like it. The problem seems to be the
function LLVMGlobalGetValueType(). I can see that that was only added
to the C API in 2018, so it looks like I may need to back-port that
(trivial) wrapper into our own llvmjit_wrap.cpp for LLVM < 8.