Build broken when using FreeBSD's make instead of gnu make
Summary
After b42681c4, the build is broken in both main and v9_18 branches.
BIND version used
Anything after b42681c4
Steps to reproduce
Build with FreeBSD's make.
What is the current bug behavior?
reading sources... [ 73%] named-nzd2nzf
reading sources... [ 76%] named-rrchecker
reading sources... [ 79%] named.conf
reading sources... [ 82%] nsec3hash
reading sources... [ 85%] nslookup
reading sources... [ 88%] nsupdate
reading sources... [ 91%] rndc
reading sources... [ 94%] rndc-confgen
reading sources... [ 97%] rndc.conf
reading sources... [100%] tsig-keygen
Warning, treated as error:
../../bin/delv/delv.rst:105:Undefined substitution referenced: "bind_keys".
*** Error code 2
Stop.
make[5]: stopped in /wrkdirs/usr/ports/dns/bind-tools/work/bind9-23cb022247e414bb99d901ed5de0f8f0bc9b9b90/doc/man
*** Error code 1
Stop.
make[4]: stopped in /wrkdirs/usr/ports/dns/bind-tools/work/bind9-23cb022247e414bb99d901ed5de0f8f0bc9b9b90/doc
*** Error code 1
What is the expected correct behavior?
Well, it shoud be building fine.
Possible fixes
Using GNU Make to build when build the docs works, but it is suboptimal.