Disappearing development installation images

[Ludovic Courtès]

Hello Guix!

We got a couple more reports that installation images at
<https://guix.gnu.org/en/download/latest/> would disappear.

After investigating, it turns out we had a periodic job on berlin
removing GC roots for *.iso and *.qcow2—no wonder they’d disappear
earlier than expected.  That job was added at a time where we had disk
space issues that have since been resolved.

I’ve reconfigured berlin with this commit:

  
https://git.savannah.gnu.org/cgit/guix/maintenance.git/commit/?id=489fc437c7b3aa0af41a40d6090eb4c51ced0028

… and ran ‘herd restart mcron’.  So from now on, those GC roots will
remain until for 30 days, the default value of ‘ttl’ in
‘cuirass-configuration’:

  
https://guix.gnu.org/manual/devel/en/html_node/Continuous-Integration.html#Cuirass

Ludo’.