Enable support for chroots using ZFS shapshots/clones

Packages describing “zfs” as local USE flag

Package “zfs” Flag Description
dev-util/schroot Enable support for chroots using ZFS shapshots/clones
app-emulation/libvirt Enable ZFS backend storage sys-fs/zfs
dev-libs/raft ZFS support
sys-cluster/ceph Add zfs support

All packages providing a “zfs” USE flag (3)