Why no builtin.mk for net/unbound?

[Stephen Borrill <netbsd%precedence.co.uk@localhost>]

When building net/lua-unbound, it unconditionally builds net/unbound even 
on a machine with unbound in base, presumably for libunbound

pkgsrc has /usr/pkg/lib/libunbound.so.8.1.37
base has /usr/pkg/lib/libunbound.so.9.0 (NetBSD 10.1_STABLE and 
11.0_STABLE)

The pkgsrc version is a newer minor version:

% grep UNBOUND_VERSION  /usr/pkg/include/unbound.h
#define UNBOUND_VERSION_MAJOR 1
#define UNBOUND_VERSION_MINOR 25
#define UNBOUND_VERSION_MICRO 1
% grep UNBOUND_VERSION /usr/include/unbound.h
#define UNBOUND_VERSION_MAJOR 1
#define UNBOUND_VERSION_MINOR 9
#define UNBOUND_VERSION_MICRO 1

Is base unbound not good enough to be worth the effort of a builtin.mk?

--
Stephen