I find all last versions of cyrus-sasl ebuilds including current stable cyrus-sasl-2.1.28-r4.ebuild have a line: berkdb? ( >=sys-libs/db-4.8.30-r1:4.8[${MULTILIB_USEDEP}] ) ... which means having selected 'berkdb' flag I always needed to build db:4.8 though my system already had db:5.3. I think it's a bug. Maybe it should be changed to smth like: berkdb? ( >=sys-libs/db-4.8.30-r1:=[${MULTILIB_USEDEP}] )