avoid building proof trees in select

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -3554,7 +3554,7 @@ pub fn dump_proof_tree<'tcx>(o: &Obligation<'tcx, ty::Predicate<'tcx>>, infcx: &
             .1
             .expect("proof tree should have been generated");
         let mut lock = std::io::stdout().lock();
-        let _ = lock.write_fmt(format_args!("{tree:?}"));
+        let _ = lock.write_fmt(format_args!("{tree:?}\n"));
         let _ = lock.flush();
     });
 }