owlman should clean up its temporary files in /tmp/owlman-aur/

[korakinos]

At present, owlman does not seem to ever delete the build directories and files in /tmp/owlman-aur/ . This can lead to the system running out of /tmp space, if you build sufficiently many (or large) packages without rebooting.

The same may be true for the files in /tmp/owlman-abs (untested).

[cdown]

I think it would be better to just have a switch for this.