how to restrict Dependency to certain architectures?

[Ralf Treinen <treinen@debian.org>]

Hi,

the packaging manual (v 3.2.1.0) says in section 8.1:

  All fields that specify BUILD-TIME relationships [...] may be restricted to
  a certain set of architectures. [emphasis by me]

>From this I conclude that it is not possible to have a (binary) dependency
relationship restricted to a certain architecture. Is this reading correct,
and if yes, is there a way to bypass this?

Here is why I want binary dependency restricted to certain architectures:
I'm maintaining a package (bibtex2html) that needs the ocaml compiler to build.
The ocaml compiler, however, compiles to native code only on some
architectures. On others (in particular mk68) it compiles only to
ocaml byte code. Hence, on the latter architectures, my package would
have to depend on the ocaml package, while this is not necessary on
the former ones. The ocaml package is quite large (14MB) and a user
(rightfully) complained to me that he wouldn't want to install the
ocaml package when it is not necessary. Splitting the ocaml package
into runtime and devel would help but still doesn't completely solve
the problem.