Add genf90 resource for cprnc to allow offline builds

[AlexanderRichert-NOAA]

Description

This PR, based on main spack commit f552dbd19918b6c928dd482e1de92d920902f1f3 (spack/spack#42015), add a genf90 resource for cprnc to allow pre-fetching for offline builds.

Issue(s) addressed

Addresses https://github.com/JCSDA/spack-stack/issues/934

Dependencies

none

Impact

none

Checklist

• [x] I have performed a self-review of my own code
• [x] I have made corresponding changes to the documentation
• [x] I have run the unit tests before creating the PR