Merge branch 'art-fixenvvar' into '21.0'

Setting AtlasVersion to timestamp for ART_local jobs

See merge request atlas/athena!8884

Former-commit-id: 3af87d98

Tools/ART/scripts/art-task-build.sh

@@ -37,6 +37,7 @@ export AtlasBuildBranch=$BRANCH
 export AtlasProject=$PROJECT
 export ${AtlasProject}_PLATFORM=$PLATFORM
 export AtlasBuildStamp=$DATESTAMP
+export AtlasVersion=${AtlasBuildStamp}
 
 ART_DIRECTORY=`which art.py`
 ART_VERSION=`art.py --version`