[master] add LDADD for libdns which is needed by the tsig support

src/lib/acl/tests/Makefile.am

@@ -31,6 +31,7 @@ run_unittests_LDADD += $(top_builddir)/src/lib/util/unittests/libutil_unittests.
 run_unittests_LDADD += $(top_builddir)/src/lib/acl/libacl.la
 run_unittests_LDADD += $(top_builddir)/src/lib/util/libutil.la
 run_unittests_LDADD += $(top_builddir)/src/lib/cc/libcc.la
+run_unittests_LDADD += $(top_builddir)/src/lib/dns/libdns++.la
 run_unittests_LDADD += $(top_builddir)/src/lib/log/liblog.la
 run_unittests_LDADD += $(top_builddir)/src/lib/exceptions/libexceptions.la
 run_unittests_LDADD += $(top_builddir)/src/lib/acl/libdnsacl.la