bug#53210: installer: referring to N-1 guix is problematic.

[Mathieu Othacehe]

Hello,

If I download the latest installer and use it to install a new system,
the "guix system init" command will install the guix package defined in
the (gnu packages package-management) module.

That means that if the installer is built with a guix package at the
version N in that module, the guix installed by the installer will be at
version N-1.

Besides the fact it is quite disturbing there are at least two major
issues:

* If the guix package is broken, it needs to build updated twice. I
  recently added a comment about that:

--8<---------------cut here---------------start------------->8---
;; If you are updating this package because it fails to build, you need to
;; actually update it *twice*, as the installer is pointing to the N-1 guix
;; package revision.
--8<---------------cut here---------------end--------------->8---

* When the guix package is updated twice in two separate but near
  commits, Cuirass that is checkouting Guix every 5 minutes might miss
  the intermediate version of the guix package. Hence, the installation
  is taking a while because the guix package is expensive to build.

Any idea on how to improve this inception problem?

Thanks,

Mathieu