> Not clear what you mean by "modules", most modules dont have to be built,
so 
> if you dont want them just delete the "lib" directory.

There are a lot of names for that, modules, extensions, libraries, external
libraries. I was referring to all extensions to the core language, like IO,
network etc. I don't need anything besides the core language, the scripts
will run in a controlled environment and can't be able to load external
scripts or make network connections.

Fancy extensions like Complex numbers (just an example, I'm not sure Ruby
has a class for that) are not wanted also, I want to have the executable as
small as possible.

Regards,

Andre de Leiradella