This also lets ant print a message pointing to this artifact and
explaining the files inside briefly. To make sure this is only printed
inside the github action, an extra `-D` option is passed to `ant test`
from the workflow file.
To allow `if` / `unless` on the echo element, this adds some namespace
definitions (this allows them on *any* element, not just the ones that
explicitly allow it). See https://ant.apache.org/manual/ifunless.html
bdfa7f305c