Use extern

Author: febo

crates/five8_core/src/lib.rs

@@ -1,7 +1,8 @@
 #![doc = include_str!("../README.md")]
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
-// Support using the crate without the standard library.
-#![cfg_attr(not(feature = "std"), no_std)]
+#![no_std]
+#[cfg(feature = "std")]
+extern crate std;
 
 #[cfg(feature = "std")]
 use core::fmt;