Can't get LuaJIT version

[averms]

When inspecting jit.version inside the Lua REPL example, I get "LuaJIT 2.1.ROLLING" instead of a specific release timestamp. For example, LuaJIT installed from my distro gives "LuaJIT 2.1.1744318430".

The LuaJIT build system uses either git or the .relver file to get the minor release version. There is no git repo in the published crate so we need to make sure .relver contains the commit timestamp. I think the easiest way to do this might be to ditch git submodules and extract the LuaJIT tarball from GitHub.