[Omake] Using Target outside of a rule body?

[Mike Furr]

I have an OCaml project which spans several directories.  To build the
final executable, I would like to just pass the "main" file and have
OMake figure out all of the object files that need to be linked in.
Something like:

foo: $(filter %.cmx, $(target main.cmx).build-deps)
   $(OCAMLOPTLINK) -o $@ $(file-sort .BUILDORDER, $+)

However, attempts to use the Target object in the rule declaration gives
the error "this function can be called only in rule bodies".

Is there any way to do this?

Thanks,
-Mike