Geiser and Guix - how to avoid long compilation steps?

[Jonathan Frederickson <jonathan@terracrypt.net>]

I've been using Geiser to hack on Guix lately, which is absolutely 
wonderful to use when it works. The trouble is, after I upgrade my 
system's Guix, Guile attempts to compile large portions of Guix when I 
attempt to switch to the module I'm working on in Geiser, e.g.:

M-x run-guile
,m (gnu services games)

This despite the fact that I'm working on a copy of Guix that I've 
already compiled with 'make' and that has the compiled copy alongside 
the source. The compilation step takes a *long* time on my hardware, 
which is fairly painful when I want to hack on Guix.

I do have my Guix checkout in geiser-guile-load-path in my emacs config 
as per https://guix.gnu.org/manual/en/html_node/The-Perfect-Setup.html:

(with-eval-after-load 'geiser-guile
  (add-to-list 'geiser-guile-load-path "~/sources/guix"))

My guess is that Guile is picking up my system's version of Guix before 
my local copy. I understand that I could start a version of Emacs in a 
pure ad-hoc environment (and Guile doesn't appear to start recompiling 
Guix when I do so), but the typical Emacs workflow is to have a 
long-running Emacs session and use that for everything; that's what I'm 
used to, and I'd like to continue to do so if possible.

Does anyone else experience this? What's the best way to use Geiser to 
hack on Guix when running Guix System?