don't refer to non-existent feature 'OdfWriter', and test these
classes if we have a developer build.
Change-Id: I59b0d4bbba4958ed3bd76f504cd8b493dbd7f877
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>