Make DUB a proper order-only dependency

Author: wilzbach

posix.mak

@@ -850,14 +850,17 @@ $(ASSERT_WRITELN_BIN)_test: assert_writeln_magic.d $(DUB) $(STABLE_DMD)
 	$(DUB) -v build --single --compiler=$(STABLE_DMD) --build=unittest $<
 	@mv ./assert_writeln_magic $@
 
-$(PHOBOS_FILES_GENERATED): $(PHOBOS_DIR_GENERATED)/%: $(PHOBOS_DIR)/% $(DUB) $(ASSERT_WRITELN_BIN)
+$(PHOBOS_FILES_GENERATED): $(PHOBOS_DIR_GENERATED)/%: $(PHOBOS_DIR)/% | $(DUB) $(ASSERT_WRITELN_BIN)
 	@mkdir -p $(dir $@)
 	@if [ $(subst .,, $(suffix $@)) = "d" ] && [ "$@" != "$(PHOBOS_DIR_GENERATED)/index.d" ] ; then \
 		$(ASSERT_WRITELN_BIN) -i $< -o $@ ; \
 	else cp $< $@ ; fi
 
-$(PHOBOS_STABLE_FILES_GENERATED): $(PHOBOS_STABLE_DIR_GENERATED)/%: $(PHOBOS_STABLE_DIR)/% $(DUB) $(ASSERT_WRITELN_BIN)
+$(PHOBOS_STABLE_FILES_GENERATED): $(PHOBOS_STABLE_DIR_GENERATED)/%: $(PHOBOS_STABLE_DIR)/% | $(DUB) $(ASSERT_WRITELN_BIN)
 	@mkdir -p $(dir $@)
+	echo "foo"
+	echo $@
+	exit 1
 	@if [ $(subst .,, $(suffix $@)) = "d" ] && [ "$@" != "$(PHOBOS_STABLE_DIR_GENERATED)/index.d" ] ; then \
 		$(ASSERT_WRITELN_BIN) -i $< -o $@ ; \
 	else cp $< $@ ; fi