This is a variable data, and not the kdesrc-build/kde-builder code itself.
Keeping it in repo-metadata will eliminate the need of manual syncing of the common resource for kdesrc-build/kde-builder. The metadata is updated at each run of script. So this will additionally make these definitions considered as always updated at users side, without the need to remember to update the kdesrc-build/kde-builder from time to time.

Later, something like "metadata version" could be introduced, for example when changes in metadata require the kdesrc-build/kde-builder update.