so I had an old config.h lying around which made the compiler believe
that the system doesn't have sys/un.h.
/usr/src/usr.sbin/nsd/remote.c:2377:8: error: use of undeclared identifier
'use_systemd'
(void)use_systemd;
^
1 error generated.
however, use_systemd doesn't exist anyway in global scope, just
dropping it is probably correct. I'm fresh out of systems that support
systemd but don't have sys/un.h to test on though 
diff --git remote.c remote.c
index 24486e37..a4934c30 100644
--- remote.c
+++ remote.c
@@ -2390,7 +2390,6 @@ err:
return -1;
#else
- (void)use_systemd;
(void)path;
log_msg(LOG_ERR, "Local sockets are not supported");
*noproto = 1;