getting the -B topdir for a GHC-API app

[Mathew Mills]

What is the "right" way to get the topDir for use with the GHC API.   
I have a little app that I would like to cabalize and release, but I  
am not sure what is the approved way of getting the '-B' option set-up.

I think it would be great if I could use template-haskell to insert  
the topDir from the ghc used to compile the app, but I am not sure  
how to get the topDir from the compiler.  Is this possible?

Does cabal already provide a means to install a "driver" script like  
that used for the ghc suite?


Also, I am looking for a code-review.  If you have some time, I would  
love some "style" guidance.

The work in progress can be found here:
    http://mathewmills.com/runTests/runTests.lhs