Enable backup service support

Packages describing “backup” as local USE flag

Package “backup” Flag Description
net-mail/cyrus-imapd Enable backup service support
dev-db/mariadb Build mariadb-backup which supports SST and hot backup of InnoDB, Aria and MyISAM including compression and encryption
dev-libs/aws-sdk-cpp AWS Backup is a fully managed backup service

All packages providing a “backup” USE flag (2)