+# Below we are using 'drv' and 'out' to contain store file names. If 'drv'
+# and 'out' are environment variables, 'list-runtime-roots' will "see" them
+# and thus prevent $drv and $out from being garbage-collected. Using 'unset'
+# allows us to make sure these are truly local shell variables and not
+# environments variables.
+unset drv
+unset out
+