Basically the RPM cannot be built on any platform except
alpha because it uses %define for library versioning, and
puts these inside %ifarch conditionals.

A quote from Jeff Johnson from the rpm-list on this very
topic...

Jeff Johnson wrote:
> I think what's happening is that you have
>
>         %ifos Linux
>         %define myvariable      a Linux value
>         %else
>         %define myvariable      a non-Linux value
>         %endif
>
> which isn't going to work since macro definitions are
currently entirely
> context free. That means that %define will be parsed and
recognized in
> comments, inside quotes, in the false branch of %if
clauses, everywhere.