Documentation about RHSCL should contain note about how users can rebuild collections: Since <collection>-build packages are not provided, if someone wants to rebuild the collection (and doesn't/can't use rpmbuild --define 'scl foo'), he first must rebuild the metapackage, which will give him <collection>-build rpm, that is the same as what we used for building.
A new section was added to the Release Notes. The book has been republished so I'm closing this bug. Thanks!
It may be worth it, although just "rebuilding" would be a very short section :)