sandbox: Don't make overlay an absolute path if tmpfs

Fixes #4039

diff --git a/mkosi/sandbox.py b/mkosi/sandbox.py
index 22829b90dd017b0403b257ca624c9994970df2c9..66e8538fc30b056779a8453a2d9804d9c14233a3 100755 (executable)
--- a/mkosi/sandbox.py
+++ b/mkosi/sandbox.py
@@ -1102,7 +1102,9 @@ def main(argv: list[str] = sys.argv[1:]) -> None:
         elif arg == "--overlay-lowerdir":
             lowerdirs.append(os.path.abspath(argv.pop()))
         elif arg == "--overlay-upperdir":
-            upperdir = os.path.abspath(argv.pop())
+            upperdir = argv.pop()
+            if upperdir != "tmpfs":
+                upperdir = os.path.abspath(upperdir)
         elif arg == "--overlay-workdir":
             workdir = os.path.abspath(argv.pop())
         elif arg == "--overlay":