Auto merge of rust-lang#85458 - jackh726:rollup-zvvybmt, r=jackh726

Rollup of 8 pull requests

Successful merges:

 - rust-lang#83366 (Stabilize extended_key_value_attributes)
 - rust-lang#83767 (Fix v0 symbol mangling bug)
 - rust-lang#84883 (compiletest: "fix" FileCheck with --allow-unused-prefixes)
 - rust-lang#85274 (Only pass --[no-]gc-sections if linker is GNU ld.)
 - rust-lang#85297 (bootstrap: build cargo only if requested in tools)
 - rust-lang#85396 (rustdoc: restore header sizes)
 - rust-lang#85425 (Fix must_use on `Option::is_none`)
 - rust-lang#85438 (Fix escape handling)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

core/src/lib.rs

@@ -113,7 +113,7 @@
 #![cfg_attr(bootstrap, feature(doc_spotlight))]
 #![cfg_attr(not(bootstrap), feature(doc_notable_trait))]
 #![feature(duration_consts_2)]
-#![feature(extended_key_value_attributes)]
+#![cfg_attr(bootstrap, feature(extended_key_value_attributes))]
 #![feature(extern_types)]
 #![feature(fundamental)]
 #![feature(intra_doc_pointers)]

core/src/option.rs

@@ -209,7 +209,7 @@ impl<T> Option<T> {
     /// assert_eq!(x.is_none(), true);
     /// ```
     #[must_use = "if you intended to assert that this doesn't have a value, consider \
-                  `.and_then(|| panic!(\"`Option` had a value when expected `None`\"))` instead"]
+                  `.and_then(|_| panic!(\"`Option` had a value when expected `None`\"))` instead"]
     #[inline]
     #[rustc_const_stable(feature = "const_option", since = "1.48.0")]
     #[stable(feature = "rust1", since = "1.0.0")]

std/src/lib.rs

@@ -268,7 +268,7 @@
 #![feature(exact_size_is_empty)]
 #![feature(exhaustive_patterns)]
 #![feature(extend_one)]
-#![feature(extended_key_value_attributes)]
+#![cfg_attr(bootstrap, feature(extended_key_value_attributes))]
 #![feature(fn_traits)]
 #![feature(format_args_nl)]
 #![feature(gen_future)]