I decided to add some flags to control the way that C source file is compiled (i.e. something like use-clang, use-intel etc.).
C-Sources: c_lib/tiger.c
There really doesn't seem to be any way to specify this in a .cabal file; the only thing we seem to have at the moment that would be even remotely useful here is --with-=path.
--with-=path
I suggest you try filing a ticket against Cabal on the trac.