Improve archiving of architecture-independent artifacts
Archive everything in ${buildApkDir} after removing artifacts we don't need. Archive the app-specific version.gradle file (e.g. for Itinerary) if it exists.
This fixes failed tar commands for apps which do not have ${buildDir}/*.gradle or ${buildApkDir}/src, e.g. KAlgebra or KTuberling.
Tested with Itinerary (https://invent.kde.org/pim/itinerary/-/pipelines/343980) and KTuberling (https://invent.kde.org/games/ktuberling/-/pipelines/343969).