Suppress some cfg from being shown in the stdlib docs

library/std/src/lib.rs

@@ -193,7 +193,10 @@
     html_playground_url = "https://play.rust-lang.org/",
     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
     test(no_crate_inject, attr(deny(warnings))),
-    test(attr(allow(dead_code, deprecated, unused_variables, unused_mut)))
+    test(attr(allow(dead_code, deprecated, unused_variables, unused_mut))),
+)]
+#![cfg_attr(not(bootstrap),
+    doc(cfg_hide(not(test), not(any(test, bootstrap))))
 )]
 // Don't link to std. We are std.
 #![no_std]
@@ -263,6 +266,7 @@
 #![feature(custom_test_frameworks)]
 #![feature(decl_macro)]
 #![feature(doc_cfg)]
+#![cfg_attr(not(bootstrap), feature(doc_cfg_hide))]
 #![feature(doc_keyword)]
 #![feature(doc_masked)]
 #![feature(doc_notable_trait)]