use -b option to dch for debian packages
the nightly build packages use a prerelease versioning scheme to ensure that they are a lower version that release builds, this causes a problem for testing release builds as the version used is less then the release version and the packaging scripts fail. the use of the -b option to dch ensure that this is only considered a warning.
this needs to be addressed in a better way but progress needs to be made now.
[ci skip]