tinderbuild options

[Ade Lovett]

At present, the tinderbuild options seem to be something of a maze of  
'-longname' and environmental variables, passed from 'tc tinderbuild'  
through to portbuild, makemake, and portbuild.

I'd like to go about cleaning this up, to the point that it can be  
parsed by getopts(1), in a similar manner to all of the other entry  
points into the tinderbox.

I don't as yet have a concrete plan as to how to go about doing this  
- just wanted to push the idea out now, since I thinking the current  
scheme is causing rather more confusion (at least to me) than is  
absolutely necessary.

-aDe