hnb fails to cross build from source, because debian/rules does not
instruct the upstream build system to perform a cross build. Using
dh_auto_build largely fixes that with two exceptions. util/asc2c is run
during build and not installed, it actually needs to be exempted from
cross building. It also runs hnb to generate the documentation. I'm
attaching a patch that fixes all but the documentation issue. As a
result, hnb cross builds a lot more, but still fails in the end.
Consider this an incremental improvement. Would you mind applying the
patch?

Helmut