The ebuild for lprng doesn't include a way to compile in kerberos support (though it is trivial to do so by hacking the ebuild). I've attached a proposed new ebuild to add a USE flag for kerberos.
Created attachment 50953 [details] a new ebuild with kerberos USE flag
Created attachment 50954 [details, diff] diff against original ebuild to add kerberos USE flag
now in -r2