Warn the user if lb-dev is used for Gauss withouth --with-fortran

Hopefully keeps others from being left with a broken lb-dev area for Gauss.

@clemenci let me know what you think. I'd almost argue silently switching to with-fortan or switching + warning are even better.
Not sure what you prefer, and I don't know Gauss well enough.
But would one ever really want Gauss without --with-fortran?