Hi Paul,

> PETSc and Trilinos (and many other libraries available in Guix) can be
> compiled with several different options.
> What is the standard way to deal with this in Guix?

Normal Guix policy is as follows. If adding extra dependencies does not
significantly increase the size of the package (as reported by `guix
size <package>`), then we proceed with that. If it increases the size
significantly, then we may consider adding separate packages (such as
dealii-trilinos, etc.).

Hope that helps! :-)