-$(PKG_BUILD_DIR)/.prepared:
- rm -rf $(PKG_BUILD_DIR)
- mkdir -p $(PKG_BUILD_DIR)
+$(PKG_BUILD_DIR)/.prepared: FORCE $(DL_DIR)/$(PKG_SOURCE)
+ifeq ($(shell $(SCRIPT_DIR)/timestamp.pl -p $(PKG_BUILD_DIR) .),.)
+ @-rm -rf $(PKG_BUILD_DIR)
+ @mkdir -p $(PKG_BUILD_DIR)