Add proper cfgs for struct HirIdValidator used only with debug assertions

compiler/rustc_passes/src/lib.rs

@@ -28,6 +28,7 @@ mod debugger_visualizer;
 mod diagnostic_items;
 pub mod entry;
 mod errors;
+#[cfg(debug_assertions)]
 pub mod hir_id_validator;
 pub mod hir_stats;
 mod lang_items;