build: use own tmp directory for each target

Makefile

@@ -207,13 +207,16 @@ config: FORCE
 	+$(NO_TRACE_MAKE) defconfig OPENWRT_BUILD=0
 
 prepare-target: FORCE
-	mkdir -p $(GLUON_OPENWRTDIR)
-	for dir in build_dir dl staging_dir tmp; do \
+	rm $(GLUON_OPENWRTDIR)/tmp || true
+	mkdir -p $(GLUON_OPENWRTDIR)/tmp
+
+	for dir in build_dir dl staging_dir; do \
 		mkdir -p $(GLUON_ORIGOPENWRTDIR)/$$dir; \
 	done
-	for link in build_dir config Config.in dl include Makefile package rules.mk scripts staging_dir target tmp toolchain tools; do \
+	for link in build_dir config Config.in dl include Makefile package rules.mk scripts staging_dir target toolchain tools; do \
 		ln -sf $(GLUON_ORIGOPENWRTDIR)/$$link $(GLUON_OPENWRTDIR); \
 	done
+
 	+$(GLUONMAKE_EARLY) feeds
 	+$(GLUONMAKE_EARLY) gluon-tools
 	+$(GLUONMAKE) config
@@ -237,7 +240,9 @@ clean: FORCE
 	rm -f $(gluon_prepared_stamp)
 
 dirclean: FORCE
-	+$(SUBMAKE) dirclean
+	for dir in build_dir dl staging_dir tmp; do \
+		rm -rf $(GLUON_ORIGOPENWRTDIR)/$$dir; \
+	done
 	rm -rf $(GLUON_BUILDDIR)