Rollup merge of #129635 - compiler-errors:unsafe-blocks, r=spastorino

Use unsafe extern blocks throughout the compiler

Making this change in preparation for edition 2024.

r? spastorino

compiler/rustc_codegen_llvm/src/lib.rs

@@ -6,6 +6,7 @@
 
 // tidy-alphabetical-start
 #![allow(internal_features)]
+#![cfg_attr(bootstrap, feature(unsafe_extern_blocks))]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
 #![feature(assert_matches)]