Expose LUA_USER_H as a build option

[hubidubi13]

Lua has a define LUA_USER_H that can be used to add an extra header during compilation. This allows, for example, to override de default lua_[un]lock functions, which are quite useful in a multithreaded environment. Usually this is application specific, so it would be nice if the ziglua build module would allow passing this extra header to the lua compilation.

If this feature is considered useful, i might have a go at implementing it myself.

[natecraddock]

Yes this seems useful to me, feel free to implement it yourself if you want to. I may get around to it eventually