mock buildroot definitions

[seth vidal]

> Is the concern about yum groupinstall that it is now "conditional" 
> depending on other things that are installed, thus it is not guaranteed 
> what is actually in the buildroot.  For this reason it is safer to 
> explicitly list it somewhere?
> 

no the concern is that format for the comps.xml has changed and may
change in the future and it matters what version of yum you use with
what comps.xml format.

-sv