use helper function instead of writing rustfmt stamp by hand

src/bootstrap/src/core/build_steps/format.rs

@@ -81,7 +81,8 @@ fn update_rustfmt_version(build: &Builder<'_>) {
     let Some((version, stamp_file)) = get_rustfmt_version(build) else {
         return;
     };
-    t!(std::fs::write(stamp_file.path(), version))
+
+    t!(stamp_file.add_stamp(version).write());
 }
 
 /// Returns the Rust files modified between the `merge-base` of HEAD and