I see. I must have confused enableDebugging and separateDebugInfo.
Still, I am not sure whether stripping/not generating a build-id by default is a good idea. As I showed above, KDE’s drkonqi crashes if ncurses does not have a build-id, even though it does not actually use its debug symbols. Why would ncurses (a CLI library) matter for dr konqi anyway?
I think some KDE maintainer should step into the discussion.
EDIT: it seems this bug was solved upstream 2 years ago, but it never made it to any KDE release for some reason (edit2: apparently the author of that commit backtracked and stated this is expected behaviour). I guess this can be closed.