Don't evaluate the sanitizer attribute if no sanitizer is enabled

This is just logical as the attribute has anyways no effect in that
case.

Author: 1c3t3a

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -630,6 +630,11 @@ fn parse_sanitize_attr(
 }
 
 fn disabled_sanitizers_for(tcx: TyCtxt<'_>, did: LocalDefId) -> SanitizerSet {
+    // No need to evaluate the sanitizer attribute if no sanitizer is enabled.
+    if tcx.sess.opts.unstable_opts.sanitizer.is_empty() {
+        return SanitizerSet::empty();
+    }
+
     // Backtrack to the crate root.
     let disabled = match tcx.opt_local_parent(did) {
         // Check the parent (recursively).