Install the configuring 'guix' into system/root profile

[Felix Lechner]

Hi,

A few months ago, someone (maybe Ludovic) posted here or on Mastodon
about how to install the 'guix' executable that was used to reconfigure
a system into that system's system (or root) profile.  Unfortunately, I
can no longer find it.  Does anyone else remember it?  Thanks!

Kind regards,
Felix

P.S. I think that setting should be the default.