Generalize package builds and virtualenv creation

Issue #338 on hold
Oliver Bestwalter
created an issue

This can serve as a meta issue collecting some outstanding issues that would be fixed by this.

The approach is to write documentation with examples for this and having a discussion around this in this issue.

There is also a draft with some discussion notes which can be used to flesh out the documentation for the functionality in doc/drafts/extend-envs-and-packagebuilds.md

related issues:

  • Handle mutliple backends for virtual environments (#313)
  • Support conda envs when using Miniconda (#273)