tcldom build failure

[Michael Thomas <wart kobold org>]

I recently built tclxml for EPEL4 and 5, and now I want to build tcldom, 
which BuildRequires: tclxml-devel.  The problem is that when I try to 
build i386 tcldom on a x86_64 build host, mock pulls in the x86_64 build 
of tclxml-devel, not the i386 build:

http://www.kobold.org/~wart/fedora/root.log (line 250)

Here is my epel4 mock config:
http://www.kobold.org/~wart/fedora/epel4.cfg

I also tried using 'setarch i686 mock -r epel4 
tcldom-3.1-10.el4.src.rpm', but that didn't change anything.

I've never seen this problem before when building other 32-bit packages 
for EPEL or Fedora on a 64-bit build host.  How can I get mock to pick 
up the i386 package and not the x86_64 package?

--Wart