add _build dir to nightlies

Makefile

@@ -213,7 +213,7 @@ package_unix:
 	rm -rf $(PACKAGE_FILE_NAME) $(PACKAGE_FILE_NAME).tar.gz
 	# Copy the package contents to $(PACKAGE_FILE_NAME)
 	mkdir -p $(PACKAGE_FILE_NAME)
-	cp -r $(OUTPUT) haxelib$(EXTENSION) std extra/LICENSE.txt extra/CONTRIB.txt extra/CHANGES.txt $(PACKAGE_FILE_NAME)
+	cp -r $(OUTPUT) haxelib$(EXTENSION) std extra/LICENSE.txt extra/CONTRIB.txt extra/CHANGES.txt _build $(PACKAGE_FILE_NAME)
 	# archive
 	tar -zcf $(PACKAGE_OUT_DIR)/$(PACKAGE_FILE_NAME)_bin.tar.gz $(PACKAGE_FILE_NAME)
 	rm -r $(PACKAGE_FILE_NAME)