contrib/guix.README test environment with guix in it

[Calvin Heim]

Hi gnunet developers,

In contrib/guix.README, the given test environment command builds an environment
with guix in it, e.g.

$ guix environment --load-path=<gnunet.git>/contrib/guix.scm --ad-hoc guix

 What is the purpose of having guix in the test environment? I usually only use
guix outside of test environments created by `guix environment', so I would like
to learn about the use case implied here.

Sincerely,
Calvin