Support LuaJIT

[dbready]

Amazing project. I love the idea of getting more things into Zig.

I saw you are hosting Lua 5.4 inside the project. Is there anything that would prevent running LuaJIT as an alternative? LuaJIT is a significantly faster runtime (admittedly, if you care about speed you don't use an interpreter language) which would make this even more appealing to me.

Downsides of LuaJIT: no real integers and no built-in UTF8 support, so that could make the interface more complicated.

[ranciere]

It's absolutely feasible, a compile-time switch would be the best.

[Ristovski]

I can confirm that Zoltan works with LuaJIT2.

The way I got this working was by first compiling LuaJIT externally with CC="zig cc" make and then linking the libluajit.a library using exe.addObjectFile("/path/to/libluajit.a");. Do note this also required defining LUAJIT_NO_UNWIND as I wasn't sure how to get libunwind working with Zig.

I also had to make a minor modification inside Zoltan to convert lua_pcallk calls to lua_pcall.

Seeing as LuaJIT has a significantly more complex build system (including invoking custom tools such as buildvm), converting this to a pure zig build will be significant work.