Dear Guix,

When loading ESS "the standard way":
  (require 'ess-site)

it fails to load because it cannot find the "etc" directory that should
ship with this package.

This patch puts that directory and its contents (as generated by the
build system) into $PROFILE/share/emacs/site-lisp/guix.d/ess/etc.

After this change, I was able to load ESS "the standard way".

Thanks for your time.

Kind regards,
Roel Janssen