Remove volumes after build

Since these volumes are both unreferencable, and should be completely
reproducible by subsequent builds, they can be safely removed.

Built on #7672
Resolves #6993 which was closed but not dealt with.
This range here is a left-over from the way the builder used to work.
It used to defer removing containers until the end of the build, now there is only ever 1 container in this map since the container is removed after each build step.