add a rustc::query_stability lint

compiler/rustc_trait_selection/src/lib.rs

@@ -22,6 +22,7 @@
 #![feature(crate_visibility_modifier)]
 #![feature(control_flow_enum)]
 #![recursion_limit = "512"] // For rustdoc
+#![cfg_attr(not(bootstrap), allow(rustc::potential_query_instability))]
 
 #[macro_use]
 extern crate rustc_macros;