[buildcentos@quark SPECS]$ rpmbuild -bp kernel-2.6.spec error: Architecture is not included: i386
Woops, my fault. That should be rpmbuild -bp --target=i686 (or x86_64 depending on what you're using) kernel-2.6.spec
Cascading problem set. Redo everything again (sorry) with that command instead, and it should work. You'll also have to pass in the --target=i686 when you do the final rpmbuild --rebuild buildroot/SRPMS/kernel-foo.src.rpm also.