[shill] openvpn depends on dbus headers

BUG=None
TEST=unit

Change-Id: Ida22969cf571a5434020d2d8e49dd36d14c2006a
Signed-off-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/35702
Reviewed-by: Bryan Freed <bfreed@chromium.org>
Reviewed-by: Darin Petkov <petkov@chromium.org>
diff --git a/Makefile b/Makefile
index 6ffc2fc..6744e44 100644
--- a/Makefile
+++ b/Makefile
@@ -474,6 +474,9 @@
 $(NSS_GET_CERT_BIN): $(NSS_GET_CERT_MAIN_OBJ) $(NSS_GET_CERT_OBJS) $(SHILL_LIB)
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $^ $(NSS_GET_CERT_LIBS) -o $@
 
+$(OPENVPN_SCRIPT_OBJS): $(DBUS_PROXY_BINDINGS)
+$(OPENVPN_SCRIPT_MAIN_OBJ): $(DBUS_PROXY_BINDINGS)
+
 $(OPENVPN_SCRIPT_BIN): $(OPENVPN_SCRIPT_MAIN_OBJ) $(OPENVPN_SCRIPT_OBJS)
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $^ $(OPENVPN_SCRIPT_LIBS) -o $@