build: Make $(package)_*_env available to all $(package)_*_cmds

Summary:
This is a backport of core#24279
Depends on D15424

Test Plan: guix build, gitian builds

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D15425