Allow unused Tool variants

Author: Kobzol

src/bootstrap/src/core/build_steps/tool.rs

@@ -244,6 +244,7 @@ macro_rules! bootstrap_tool {
         ;
     )+) => {
         #[derive(PartialEq, Eq, Clone)]
+        #[allow(dead_code)]
         pub enum Tool {
             $(
                 $name,