GHC dies silently with faulty preprocessor

This is perhaps a minor nuisance but I had to spend
quite some time to track down my bug. When ghc is given
a preprocessor which for some reason cannot execute
then ghc just dies silently without giving any
indication as to what the problem was. It would be nice
with a little message hinting at the problem on stderr.

Oh, and by the way, the -F flag doesn't have any
documentation. It is only mentioned together with -optF.