[Makefile] distribute cg_viewer.yes.ml even if current env does not have dgraph

Makefile

@@ -785,12 +785,11 @@ PLUGIN_DIR:=src/plugins/callgraph
 PLUGIN_CMO:= options journalize subgraph cg services uses register
 ifeq ($(HAS_DGRAPH),yes)
 PLUGIN_GUI_CMO:=cg_viewer
-PLUGIN_DISTRIB_EXTERNAL:=cg_viewer.yes.ml
 PLUGIN_GENERATED:=$(PLUGIN_DIR)/cg_viewer.ml
 else
 PLUGIN_GUI_CMO:=
-PLUGIN_DISTRIB_EXTERNAL:=cg_viewer.ml
 endif
+PLUGIN_DISTRIB_EXTERNAL:=cg_viewer.yes.ml
 PLUGIN_CMI:= callgraph_api
 PLUGIN_INTERNAL_TEST:=yes
 PLUGIN_TESTS_DIRS:=callgraph