CentOS - Mar 2007 - Building i386 packages on a x86_64 system

Hi!

Is there an easy way to do that? I looked around and the way that is
usually advertised is

setarch i386 rpmbuild --target=i386 --rebuild ....

but for the SRPMs I've tried it always fails at tests in the Spec-File
(like %ifnarch x86_64)

The RPM I try to build doesn't compile anything (it just wraps a
TAR-File), so setting up mock isn't necessary in my opinion.

Is there any way to use the --target-switch?

Thanks