The advantage of this hack is that we still get to use upstream ‘guile’
for compilation purposes (with no performance hit), and we use our own
“safe” ‘guile’ executable for stuff that may use GnuTLS, in particular
‘guix substitute’ and ‘guix perform-download’.

There may still be a few cases where we’d use stock ‘guile’ together
with GnuTLS.  The only example that comes to mind is when calling
‘download-nar’ or ‘swh-download’ as a fallback in (guix git-download).
That’s quite rare though.

So I think that the above is a workaround we could deploy right away.
It should allow us to wait until we have Guile on mini-GMP.

Thoughts?

Ludo’.