Commit 9c0484d722082e016aebab6b90d7cbedec93857b added REQUIRED_USE="!gnutls? ( ssl? ( threads ) )" to net-libs/libvncserver. With defaul/linux make.defaults setting USE="ssl" it means that many users by default get unmet requirements. Two possible solutions to make this a bit more comfortable: - net-libs/libvncserver with +threads by default - 'net-libs/libvncserver threads' could be added to package.use of that profile
Fixed in 7ae0cafde9984e56566ad1bb997d039d1dad3fab.