eldritch horrorsandRaito Bezarius
c698466dc7
this makes the actual build directories used by builders invisible and
inaccessible to other processes on the system, avoiding another vector
for outside processes to interfere with builds or pass credentials the
build sandbox should not have access to into the build sandbox anyway.
fixes #919
Change-Id: Ifaa4d8e3940cfde1406e925f75c1375d2e86d81a
(cherry picked from commit 9d5a5c4dc0)