[Assist] opensysusers and systemd are in conflict

[bill-auger]

the beginner's guide is a bit outdated - it's content has
been merged into the standard install guide, which is
up-to-date:

https://wiki.parabola.nu/Installation_Guide

the command to install the most basic openrc system is:

# pacstrap /mnt base elogind

base-devel currently depends on systemd - there is a discussion
on the bug tracker about changing that; but today, you can not
install base-devel on an openrc system

https://labs.parabola.nu/issues/2638