We already have dev-java/jcalendar but it's not the same thing we need here. We would need to package http://sourceforge.net/projects/jcalendar/ but that project has stopped maintenance already. Every other bundled jar I was able to remove.
Seems like the ebuild for app-office/borg-1.7.4-r3 explicitly deletes the bundled jcalendar.jar: https://github.com/gentoo/gentoo/blob/61b861acd7b49083dab687e133f30f3331cb7480/app-office/borg/borg-1.7.4-r3.ebuild#L38-L39 Solved?
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=2ecfa4c8911969384df65fa601008e8b741aee1c commit 2ecfa4c8911969384df65fa601008e8b741aee1c Author: Jakov Smolić <jsmolic@gentoo.org> AuthorDate: 2021-11-22 09:12:00 +0000 Commit: Jakov Smolić <jsmolic@gentoo.org> CommitDate: 2021-11-22 09:13:44 +0000 app-office/borg: treeclean Closes: https://bugs.gentoo.org/819756 Closes: https://bugs.gentoo.org/706554 Closes: https://bugs.gentoo.org/174173 Signed-off-by: Jakov Smolić <jsmolic@gentoo.org> app-office/borg/Manifest | 1 - app-office/borg/borg-1.7.4-r3.ebuild | 59 ------------------------------------ app-office/borg/metadata.xml | 11 ------- profiles/package.mask | 5 --- 4 files changed, 76 deletions(-)