[bug#68347] [PATCH] gnu: Add cadical

[Max Heisinger <maximilian.heisinger@jku.at>]

Hi,

thank you for your patch-based approach Sören! I think yours is more readable
for the Makefile changes.

We could add the substitutions for 7z, xz, etc. and the changes to
scripts/make-build-header.sh in order to make the build reproducible and not
rely on runtime $PATH searches, then we'd have combined the best from both
patches - however I'd also be fine to start with my original version and add
the patch in a later revision.

I would also be happy if we could maintain a single CaDiCaL package in the main
Guix repository :)

Best,
Max