feat: refactored bootstrap files to use stderr consistently

src/bootstrap/lib.rs

@@ -686,9 +686,9 @@ impl Build {
         // Check for postponed failures from `test --no-fail-fast`.
         let failures = self.delayed_failures.borrow();
         if failures.len() > 0 {
-            println!("\n{} command(s) did not execute successfully:\n", failures.len());
+            eprintln!("\n{} command(s) did not execute successfully:\n", failures.len());
             for failure in failures.iter() {
-                println!("  - {}\n", failure);
+                eprintln!("  - {}\n", failure);
             }
             process::exit(1);
         }