Record error when setting up repo fails rather than abort entire script.

src/nix_util/high_level.rs

@@ -1,6 +1,7 @@
 use std::ffi::OsStr;
 use std::ffi::OsString;
 use std::path::Path;
+use std::process::ExitStatus;
 use std::process::Stdio;
 
 use tokio::process::Command;
@@ -19,7 +20,7 @@ pub(crate) async fn nixos_build_target<B, F, A, TN>(
     attr: A,
     target_name: TN,
     build_id: i64,
-) -> Result<()>
+) -> Result<ExitStatus>
 where
     B: AsRef<Path>,
     F: AsRef<Path>,
@@ -58,9 +59,9 @@ where
     let child = command.spawn()?;
 
     let mut running_build = RunningBuild::new(db_handle, build_id)?;
-    running_build.run_to_completion(child, target_name).await?;
+    let exit_status = running_build.run_to_completion(child, target_name).await?;
 
-    Ok(())
+    Ok(exit_status)
 }
 
 pub(crate) async fn nix_flake_update<F>(flake_path: F) -> Result<()>