[artix-general] Fixes for dbus-s6

[Yunxiang Li]

In dbus-s6 the init script overwrites /etc/machine-id everytime, however
machine-id should not change across reboots. This causes problems for programs
that expects this behavior, like pulseaudio which stores their setting in a file
named after the machine-id, therefore it will not remember the settings if
rebooted.

The fix is simple, change the second line of /etc/s6/sv/dbus-srv/run to

foreground { dbus-uuidgen --ensure=/etc/machine-id }

It might be better to use the default location for the machine-id, which is
/var/lib/dbus/machine-id and make /etc/machine-id a symlink to it, in which case
we can just use

foreground { dbus-uuidgen --ensure }

I'm not sure how would this change be done tho, at least /var/lib/dbus needs to
be created somehow.