build: make libraries self-reliant

libospf and libospfclient both need libzebra, so they should link
against it. The days of libtool propagating upwards such dependencies
are nearing their end...

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/ospfd/Makefile.am b/ospfd/Makefile.am
index 40f2cfe..f21f507 100644
--- a/ospfd/Makefile.am
+++ b/ospfd/Makefile.am
@@ -7,6 +7,7 @@
 
 lib_LTLIBRARIES = libospf.la
 libospf_la_LDFLAGS = -version-info 0:0:0
+libospf_la_LIBADD = ../lib/libzebra.la
 
 sbin_PROGRAMS = ospfd