Use Drop instead of destroy() for locks.

library/std/src/sys/unsupported/locks/condvar.rs

@@ -26,7 +26,4 @@ impl Condvar {
     pub unsafe fn wait_timeout(&self, _mutex: &Mutex, _dur: Duration) -> bool {
         panic!("condvar wait not supported");
     }
-
-    #[inline]
-    pub unsafe fn destroy(&self) {}
 }

library/std/src/sys/unsupported/locks/mutex.rs

@@ -32,7 +32,4 @@ impl Mutex {
     pub unsafe fn try_lock(&self) -> bool {
         self.locked.replace(true) == false
     }
-
-    #[inline]
-    pub unsafe fn destroy(&self) {}
 }

library/std/src/sys/unsupported/locks/rwlock.rs

@@ -62,7 +62,4 @@ impl RwLock {
     pub unsafe fn write_unlock(&self) {
         assert_eq!(self.mode.replace(0), -1);
     }
-
-    #[inline]
-    pub unsafe fn destroy(&self) {}
 }