It builds okay, but the install step fails if it can't write to /var/empty. The build log doesn't seem to say anything useful, just `!!! Cannot write to '/var/empty'.`. The ebuild attempts to `keepdir /var/empty` in src_install() (maybe that's trying to write one of those empty .keep_* files in /var/empty?); according to bug #542386, this is no longer necessary. Bug #507248 also mentions openssh modifications to /var/empty which are no longer necessary.
we probably can drop it now. the init script will create the dir if it doesn't yet exist since it's in /var.
openssh-7.5p1 no longer runs `keepdir /var/empty`