[CentOS] Problem rebuilding glibc for xen

I would like to rebuild glibc specifically with the -mno-tls-direct-seg-refs
to allow better performance with Xen.

I'm using Centos 4.2 x86_64 on an Athlon 3200+. I'm using the
2.6.9-11.106.unsupported kernel for reiser support.

My thought was to download and install the SRPM and then rpmbuild with no
changes to make sure it works before adding the above flag.

Unfortunately, the rpmbuild hangs during tst-tls9.

Has anyone else managed this?

As an alternative suggestion is there a chance that a build of glibc with
this flag could be added to centosplus? 
This would be very useful until this change makes it into the main stream.

Thanks

Daveh