Use `ManuallyDrop<T>` instead of `mem::forget` in scopeguard
Use `ManuallyDrop<T>` instead of `mem::forget` in scopeguard

With field retagging in SB, this causes UB because the read out value
is invalidated by the move into `mem::forget`. Using `ManuallyDrop<T>`
avoids the problem.

rust-lang/hashbrown,rust-lang/hashbrown