Fix build on latest nightly

src/elision.rs

@@ -5,6 +5,8 @@
 // http://opensource.org/licenses/MIT>, at your option. This file may not be
 // copied, modified, or distributed except according to those terms.
 
+#[cfg(all(feature = "nightly", any(target_arch = "x86", target_arch = "x86_64")))]
+use std::arch::asm;
 use std::sync::atomic::AtomicUsize;
 
 // Extension trait to add lock elision primitives to atomic types

src/lib.rs

@@ -11,7 +11,6 @@
 
 #![warn(missing_docs)]
 #![warn(rust_2018_idioms)]
-#![cfg_attr(feature = "nightly", feature(asm))]
 
 mod condvar;
 mod elision;