Hello!

I was getting errors like this in my GNU Guix System installation:

# cat /var/log/mcron.log
/gnu/store/8q2i735qhdivn5pn87b6ay7z16xnf6py-rottlog-
0.72.2/sbin/rottlog: line 1596: sendmail: command not found
/gnu/store/8q2i735qhdivn5pn87b6ay7z16xnf6py-rottlog-
0.72.2/sbin/rottlog: line 1596: sendmail: command not found
/gnu/store/8q2i735qhdivn5pn87b6ay7z16xnf6py-rottlog-
0.72.2/sbin/rottlog: line 1596: sendmail: command not found
/gnu/store/8q2i735qhdivn5pn87b6ay7z16xnf6py-rottlog-
0.72.2/sbin/rottlog: line 1596: sendmail: command not found
/gnu/store/8q2i735qhdivn5pn87b6ay7z16xnf6py-rottlog-
0.72.2/sbin/rottlog: line 1596: sendmail: command not found

I am guessing this means sendmail needs to be added as propagated-
inputs to ensure it is available to rottlog at runtime.

Attached patch with these changes!

Thank you!