fix: use TMPDIR if provided by environment

Change-Id: I421c9f65efb86406d613551f0ae08e9d9e876633

bin/yashchiki

@@ -97,7 +97,8 @@ parser.add_argument(
     help="Folder where to store meta information to be copied into the "
          "container. If not provided, a temporary directory is used.")
 parser.add_argument(
-    "--tmpdir", type=pathlib.Path, default="",
+    "--tmpdir", type=pathlib.Path,
+    default="TMPDIR" in os.environ and os.environ["TMPDIR"] or "",
     help=f"Directory in which temporary files are saved. This includes "
          "spack stages, temporary spack config as well as the meta dir "
          "(if not provided as an argument). If this argument is given "