Use Arc instead of Rc

Author: Zoxc

src/librustc_data_structures/sync.rs

@@ -177,8 +177,9 @@ cfg_if! {
 
         pub type MetadataRef = OwningRef<Box<dyn Erased>, [u8]>;
 
-        pub use std::rc::Rc as Lrc;
-        pub use std::rc::Weak as Weak;
+        pub use std::sync::Arc as Lrc;
+        pub use std::sync::Weak as Weak;
+
         pub use std::cell::Ref as ReadGuard;
         pub use std::cell::Ref as MappedReadGuard;
         pub use std::cell::RefMut as WriteGuard;