devel/dbus: create directory for machine-id

Create the directory where dbus-uuidgen is *going* to write
the machine-id, just in case -- might affect only older FreeBSD
versions. dbus-uuidgen doesn't create intermediate directories
when given an explicit path either, so it does need to be done
by the environment.

(I'm purposely not also tackling other dbus-uuidgen issues,
those are in different PRs with different assignees)

PR: 225098
Reported by: Andrey Zakharchenko