Only call default steps once, not once for each PathSet

Running steps multiple times defeats the whole point of rust-lang#96501,
since lint messages will be duplicated.

src/bootstrap/builder.rs

@@ -304,9 +304,7 @@ impl StepDescription {
         if paths.is_empty() || builder.config.include_default_paths {
             for (desc, should_run) in v.iter().zip(&should_runs) {
                 if desc.default && should_run.is_really_default() {
-                    for pathset in &should_run.paths {
-                        desc.maybe_run(builder, vec![pathset.clone()]);
-                    }
+                    desc.maybe_run(builder, should_run.paths.iter().cloned().collect());
                 }
             }
         }