Makefile: Fixed 'permission denied' error when make clean after Docke…

…r make in Ubuntu.

Makefile

@@ -120,6 +120,7 @@ gmet-linux:
 		docker build -t meta/builder:local			\
 			-f Dockerfile.metadium . &&			\
 		docker run -e HOME=/tmp --rm -v $(shell pwd):/data	\
+			-u $(shell id -u):$(shell id -g)                \
 			-w /data meta/builder:local			\
 			"git config --global --add safe.directory /data;\
 			 make USE_ROCKSDB=$(USE_ROCKSDB)";		\