Rollup merge of rust-lang#93658 - cchiw:issue-77443-fix, r=joshtriplett

Stabilize `#[cfg(panic = "...")]`

[Stabilization PR](https://rustc-dev-guide.rust-lang.org/stabilization_guide.html#stabilization-pr) for rust-lang#77443

Author: matthiaskrgr

core/tests/lib.rs

@@ -6,7 +6,7 @@
 #![feature(bool_to_option)]
 #![feature(box_syntax)]
 #![feature(cell_update)]
-#![feature(cfg_panic)]
+#![cfg_attr(bootstrap, feature(cfg_panic))]
 #![cfg_attr(bootstrap, feature(cfg_target_has_atomic))]
 #![feature(const_assume)]
 #![feature(const_black_box)]