Use the GEN silent rule when generating files with sed

src/_updown/Makefile.am

@@ -4,6 +4,7 @@ dist_man8_MANS = _updown.8
 EXTRA_DIST = _updown.in
 
 _updown : _updown.in
+	$(AM_V_GEN) \
 	sed \
 	-e "s:\@sbindir\@:$(sbindir):" \
 	-e "s:\@routing_table\@:$(routing_table):" \