fix(tvix/eval): builtins.unsafeGetAttrPos returns path as a string

Change-Id: Ia1058a5ea687f413fbb62365da199032bdbd3fd2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11155
Reviewed-by: tazjin <tazjin@tvl.su>
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>

tvix/eval/src/builtins/mod.rs

@@ -1583,7 +1583,7 @@ mod placeholder_builtins {
         let res = [
             ("line", 42.into()),
             ("col", 42.into()),
-            ("file", Value::Path(Box::new("/deep/thought".into()))),
+            ("file", Value::String("/deep/thought".into())),
         ];
         Ok(Value::attrs(NixAttrs::from_iter(res.into_iter())))
     }