Subject: Mcron logs should be rotated

From: Leo Famulari <[email-masked]>
Date: Sat, 27 Mar 2021 16:06:42 -0400

I noticed that a Guix System machine had an enormous mcron.log file
(dozens of gigabytes).

I think that the mcron-service-type should use rottlog, by default, to
rotate its log.