Remove all checks of IntrinsicDef::must_be_overridden except for the actual overrides in codegen

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -81,10 +81,6 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, _: LocalCrate) -> DefIdMap<S
                 return library.kind.is_statically_included().then_some(def_id);
             }
 
-            if tcx.intrinsic(def_id).is_some_and(|i| i.must_be_overridden) {
-                return None;
-            }
-
             // Only consider nodes that actually have exported symbols.
             match tcx.def_kind(def_id) {
                 DefKind::Fn | DefKind::Static { .. } => {}