Support for compiling and linking non-C objects (such as Fortran)

Hi,

I have some F90 code in my project that I'd like to be built and linked with the rest. Is there a way of doing this with Dune? If there is it's not obvious, neither from the documentation nor from a quick glance at the code :) Of course for C it's easy.

For reference with Oasis & Ocamlbuild I use an .f90-to-.o rule in myocamlbuild.ml and then I cheat by telling Oasis that it's C code (i.e. I say CSources: foo.c when in reality the file is foo.f90).