lib: hook libder up to the build

libder will be used in upcoming ECC support in the pkg(7) bootstrap to
read DER-encoded keys and signatures.

Differential Revision:	https://reviews.freebsd.org/D48116

share/mk/src.libnames.mk

@@ -44,6 +44,7 @@ _INTERNALLIBS=	\
 		bsnmptools \
 		c_nossp_pic \
 		cron \
+		der \
 		diff \
 		elftc \
 		fdt \
@@ -614,6 +615,9 @@ LIBTELNET?=	${LIBTELNETDIR}/libtelnet${PIE_SUFFIX}.a
 LIBCRONDIR=	${_LIB_OBJTOP}/usr.sbin/cron/lib
 LIBCRON?=	${LIBCRONDIR}/libcron${PIE_SUFFIX}.a
 
+LIBDERDIR=	${_LIB_OBJTOP}/lib/libder
+LIBDER?=	${LIBDERDIR}/libder${PIE_SUFFIX}.a
+
 LIBNTPDIR=	${_LIB_OBJTOP}/usr.sbin/ntp/libntp
 LIBNTP?=	${LIBNTPDIR}/libntp${PIE_SUFFIX}.a