Clean up crate attributes

* No need for stability marker
* Rustdoc docs not used for this crate
* Remove old build-system related cruft from rustc itself.

src/lib.rs

@@ -1,34 +1,16 @@
-#![cfg_attr(not(stage0), deny(warnings))]
-#![cfg_attr(not(test), no_std)]
 #![cfg_attr(feature = "compiler-builtins", compiler_builtins)]
-#![crate_name = "compiler_builtins"]
-#![crate_type = "rlib"]
-#![doc(
-    html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
-    html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
-    html_root_url = "https://doc.rust-lang.org/nightly/",
-    html_playground_url = "https://play.rust-lang.org/",
-    test(attr(deny(warnings)))
-)]
+#![feature(abi_unadjusted)]
 #![feature(asm)]
 #![feature(compiler_builtins)]
 #![feature(core_intrinsics)]
+#![feature(lang_items)]
+#![feature(linkage)]
 #![feature(naked_functions)]
 #![feature(repr_simd)]
-#![feature(abi_unadjusted)]
-#![feature(linkage)]
-#![feature(lang_items)]
-#![allow(unused_features)]
 #![no_builtins]
-#![cfg_attr(feature = "compiler-builtins", feature(staged_api))]
-#![cfg_attr(
-    feature = "compiler-builtins",
-    unstable(
-        feature = "compiler_builtins_lib",
-        reason = "Compiler builtins. Will never become stable.",
-        issue = "0"
-    )
-)]
+#![no_std]
+
+#![allow(unused_features)]
 
 // We use `u128` in a whole bunch of places which we currently agree with the
 // compiler on ABIs and such, so we should be "good enough" for now and changes