We used to build both base and patch bundles for a base release such as 5.0 and 6. We would also build base and patch bundles for update releases.

In Mustang at some point, we realized that there is no point in building patch and base bundles for both base and patch releases. So we now only do the following:

base release (5.0, 6, 7....) only build the base images
update releases (5.0uX, 6uX, 7uX) only build patch releases

Because of this, there really is no need to have the NO_RTPATCH variable. Users will need rtpatch to build an update release, but they will not need it to build a base release.