functional2: fix bug in physical_store_path_for()

I guess on aarch64-darwin dirs.store_dir can be a str?

Change-Id: If4baa1f48f641775c6e3ab9ce7a58e476a6a6964

tests/functional2/testlib/fixtures/nix.py

@@ -81,7 +81,7 @@ class NixSettings:
         (env.dirs.nix_conf_dir / "nix.conf").write_text(cfg)
         env.set_env("NIX_CONFIG", cfg)
         if self.nix_store_dir:
-            env.dirs.nix_store_dir = str(self.nix_store_dir)
+            env.dirs.nix_store_dir = self.nix_store_dir
 
 
 @dataclasses.dataclass

tests/functional2/testlib/fixtures/test_nix.py

@@ -74,4 +74,4 @@ def test_nix_settings_to_env_overlay_store_dir(tmp_path: Path):
 
     settings.to_env_overlay(env)
     assert "store = " not in env._env["NIX_CONFIG"]
-    assert env.dirs.nix_store_dir == "/some/path"
+    assert str(env.dirs.nix_store_dir) == "/some/path"