I looked at what kind of a difference cvs up made to built_with_use usage.

betelgeuse@pena /usr/portage $ grep --include "*.ebuild" built_with_use
-r . | wc -l
690

cvs up

betelgeuse@pena /usr/portage $ grep --include "*.ebuild" built_with_use
-r . | wc -l
708

There should be no legitimate reason for the number to go up so please
whenever bumping ebuilds, remove the usage of built_with_use.

Regards,
Petteri