Issues with running multiple tinderbuilds in parallel

[Ade Lovett]

Wanting to fully utilize my SMP tinderbox (8.0-CURRENT), I decided to  
fire off a couple of tinderbuild's in parallel.

I'm getting some occasional really strange results with false-positive  
leftovers, for example:

http://tinderbox.lovett.com/logs/5-i386/autoconf-2.61_2.log

or, for a little less extreme example:

http://tinderbox.lovett.com/logs/6-i386/gnome-desktop-2.20.3.log


This is using nullfs, with only the distfiles being from a NFS-mounted  
location.  Using NFS actually causes the machine to pretty  
consistently lock up with NFS server not responding and processes  
going unkillable, resulting in having to powercycle the machine.

Looks like something, somewhere, is not doing a proper cleanup job  
(most likely contender is buildscript), but I'm at a complete loss as  
to what exactly is happening.

-aDe