feat(tvix/nix-compat): Use StorePath in Output

https: //b.tvl.fyi/issues/264
Change-Id: Icb09be9643245cc68d09f01d7723af2d44d6bd1a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11001
Autosubmit: Peter Kolloch <info@eigenvalue.net>
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

tvix/glue/src/tvix_build.rs

@@ -52,7 +52,7 @@ pub(crate) fn derivation_to_build_request(
     let mut output_paths: Vec<String> = derivation
         .outputs
         .values()
-        .map(|e| e.path[1..].to_owned())
+        .map(|e| e.path_str()[1..].to_owned())
         .collect();
 
     // Sort the outputs. We can use sort_unstable, as these are unique strings.