stumpwm contrib modules have been broken

[Katherine Cox-Buday]

Sometime recently, the way Common Lisp code is compiled was changed (for
the better, I think), and now my StumpWM contrib modules won't load.
Here's why:

StumpWM looks[1] for .asd files to determine what is a module. Guix's
Common Lisp build system used to combine an entire system into a single
.fasl file and then produce a .asd file for loading it. Now -- as far as
I can tell -- it looks like `lib/common-lisp/sbcl` is more like the
Common Lisp cache: one .fasl file per .lisp file.

If I point StumpWM at `lib/common-lisp/sbcl` via `set-module-dir`, it
finds no modules. If I point StumpWM at `share/common-lisp/sbcl`, it
finds modules, tries to compile them, and then gives me a permissions
error about writing to the `/gnu` store.

Is anyone using StumpWM contrib modules successfully with Guix's new
layout? How?

[1] - https://github.com/stumpwm/stumpwm/blob/master/module.lisp#L70

-- 
Katherine