Conditionalize wrap(3) use based on MK_TCP_WRAPPERS instead of

always building support into ypserv.

MFC after:	2 weeks

usr.sbin/ypserv/Makefile

@@ -1,5 +1,7 @@
 # $FreeBSD$
 
+.include <src.opts.mk>
+
 RPCDIR=	${.CURDIR}/../../include/rpcsvc
 .PATH: ${RPCDIR} \
        ${.CURDIR}/common
@@ -10,11 +12,14 @@ SRCS=	yp_svc.c yp_server.c yp_dblookup.c yp_dnslookup.c \
 	ypxfr_clnt.c yp.h yp_main.c yp_error.c yp_access.c yp_svc_udp.c \
 	yplib_host.c
 
-CFLAGS+= -DDB_CACHE -DTCP_WRAPPER -I.
+CFLAGS+= -DDB_CACHE -I.
 
 WARNS?=	0
 
-LIBADD=	wrap
+.if ${MK_TCP_WRAPPERS} != "no"
+CFLAGS+=	-DTCP_WRAPPER
+LIBADD+=	wrap
+.endif
 
 CLEANFILES= yp_svc.c ypxfr_clnt.c yp.h