[Buildroot] LIBFOO_SITE in .mk file

[Jeff Krasky]

> Those are not Buildroot variables, but Kbuild variables, that you must
> pass when running the modules_install. The fact that EtherCAT contains
> kernel modules makes it not completely straightforward to package.

At what point is modules_install being run?

> Do you need it right now ? I might be interested in helping package
> EtherCAT, but I don't have much time at the moment.

Time is very short, yes.  Anything you can do to help is definitely
appreciated.  Like, for now, can you say more about running modules_install
and passing parameters to it?

Thank you very much, again.