Auto merge of #116088 - nbdd0121:unwind, r=Amanieu,RalfJung

Stabilise `c_unwind`

Fix #74990
Fix #115285 (that's also where FCP is happening)

Marking as draft PR for now due to `compiler_builtins` issues

r? `@Amanieu`

library/core/src/lib.rs

@@ -199,13 +199,13 @@
 //
 // Language features:
 // tidy-alphabetical-start
+#![cfg_attr(bootstrap, feature(c_unwind))]
 #![feature(abi_unadjusted)]
 #![feature(adt_const_params)]
 #![feature(allow_internal_unsafe)]
 #![feature(allow_internal_unstable)]
 #![feature(asm_const)]
 #![feature(auto_traits)]
-#![feature(c_unwind)]
 #![feature(cfg_sanitize)]
 #![feature(cfg_target_has_atomic)]
 #![feature(cfg_target_has_atomic_equal_alignment)]