Some .asd definitions have dependencies (declared with
:system-depends-on).
A common dependency is prove-asdf.

If we read all .asd then we must drag all ASDF dependencies.  This can be a
burden, say, for a test system that is not supported in Guix at the moment.

My intuition is that parsing all ASD files is a good default behaviour
but we should allow to override it with the asd-files keyword.

Thoughts?

-- 
Pierre Neidhardt
https://ambrevar.xyz/