[arch-general] makechrootpkg and long union unmount time

Hello, When I'm building a package using makechrootpkg and the build fails or I happen to interrupt it, sometimes it gets stuck at the "cleaning up unioned mounts" stage for a very long time (from several seconds up to a few minutes). During this time, the disk shows intense activity. Does this happen to others too? Any idea why this is occurring and how to prevent it?