Rollup merge of #71736 - RalfJung:silence-spurious-unused, r=Mark-Simulacrum

bootstrap: also apply unused-attributes hack without deny_warnings

This is a follow-up to #70881 that also silences these warnings when deny_warnings is off. They otherwise spam my screen during development and make it hard to see actual warnings.

Cc  @eddyb r? @Mark-Simulacrum

Author: RalfJung

src/bootstrap/builder.rs

@@ -1088,13 +1088,13 @@ impl<'a> Builder<'a> {
 
             if self.config.deny_warnings {
                 rustflags.arg("-Dwarnings");
+            }
 
-                // FIXME(#58633) hide "unused attribute" errors in incremental
-                // builds of the standard library, as the underlying checks are
-                // not yet properly integrated with incremental recompilation.
-                if mode == Mode::Std && compiler.stage == 0 && self.config.incremental {
-                    rustflags.arg("-Aunused-attributes");
-                }
+            // FIXME(#58633) hide "unused attribute" errors in incremental
+            // builds of the standard library, as the underlying checks are
+            // not yet properly integrated with incremental recompilation.
+            if mode == Mode::Std && compiler.stage == 0 && self.config.incremental {
+                rustflags.arg("-Aunused-attributes");
             }
         }