Add a conditional to the Makefile to optionally install the /run/motd.d tpmfiles config

[travier]

See https://bugzilla.redhat.com/show_bug.cgi?id=2120544 and https://src.fedoraproject.org/rpms/console-login-helper-messages/pull-request/12.

Some distributions already ship the following tmpfiles.d config:

d /run/motd.d - - - - -

Thus leading to noise in the journal:

/usr/lib/tmpfiles.d/setup.conf:2: Duplicate line for path "/run/motd.d", ignoring.

So we need to add a condition or another target to the Makefile to install that optionally.

[travier]

The idea for this issue is that we want to be able to remove this line (https://src.fedoraproject.org/rpms/console-login-helper-messages/blob/rawhide/f/console-login-helper-messages.spec#_90) from the CLHM specfile in Fedora while adding an option or another make target to install fr other distributions.