Merge pull request #829 from masahir0y/build

Makefile: use git describe for BUILD_STRING

Makefile

@@ -111,7 +111,7 @@ endif
 
 # Default build string (git branch and commit)
 ifeq (${BUILD_STRING},)
-        BUILD_STRING	:=	$(shell git log -n 1 --pretty=format:"%h")
+        BUILD_STRING	:=	$(shell git describe --always --dirty --tags 2> /dev/null)
 endif
 VERSION_STRING		:=	v${VERSION_MAJOR}.${VERSION_MINOR}(${BUILD_TYPE}):${BUILD_STRING}