This ensures that we have different version numbers for different
releases without switching completely to the release service version.
This fixes problems with building flatpaks because appstream-compose
errors out if there are multiple <release> tags with the same version
attribute in the AppStream data (org.kde.kleopatra.appdata.xml).

This approach was suggested by Albert Astals Cid with reference to
khelpcenter from where I borrowed some of the code.