define required type 'MovableMutex'

Author: stlankes

library/std/src/sys/hermit/mutex.rs

@@ -155,6 +155,8 @@ pub struct Mutex {
     inner: Spinlock<MutexInner>,
 }
 
+pub type MovableMutex = Mutex;
+
 unsafe impl Send for Mutex {}
 unsafe impl Sync for Mutex {}