Creating debs using a cross-build envronment?

Hi,

I found some Debian tools to create .deb packages available, like
pdebuild-cross, buildcross, xapt, xdeb, dpkg-cross, most of them
developed by emdebian. According to your web pages all these tools seems
to create GNU/Linux packages for a specific CPU using GNU/Linux as
build/host environment. Are there tools available also for another OS,
in my case GNU/Hurd. 

Up til now I have created a cross build environment with gcc-4.4,
eglibc-2.13, gnumach and hurd libraries, etc. Next step would be to
create .debs for the target architecture. I know most packages can be
built natively, but not all, like gnat, etc.

- what is missing from the built toolset so far (binutils, etc)
- any emdebian tools usable for this, i.e. for cross OS package
building?

Please Cc: since I'm not subscribed (yet)
Thanks!