Rollup merge of #127733 - GrigorenkoPV:don't-forget, r=Amanieu

Replace some `mem::forget`'s with `ManuallyDrop`

              > but I would like to see a larger effort to replace all uses of `mem::forget`.

_Originally posted by `@saethlin` in rust-lang/rust#127584 (comment)

So,
r? `@saethlin`

Sorry, I have finished writing all of this before I got your response.

Author: matthiaskrgr

tests/fail-dep/concurrency/libc_pthread_mutex_deadlock.stderr

@@ -10,7 +10,7 @@ LL |             assert_eq!(libc::pthread_mutex_lock(lock_copy.0.get() as *mut _
 error: deadlock: the evaluated program deadlocked
   --> RUSTLIB/std/src/sys/pal/PLATFORM/thread.rs:LL:CC
    |
-LL |             let ret = libc::pthread_join(self.id, ptr::null_mut());
+LL |         let ret = unsafe { libc::pthread_join(id, ptr::null_mut()) };
    |                                                                  ^ the evaluated program deadlocked
    |
    = note: BACKTRACE:

tests/fail-dep/concurrency/libc_pthread_rwlock_write_read_deadlock.stderr

@@ -10,7 +10,7 @@ LL |             assert_eq!(libc::pthread_rwlock_wrlock(lock_copy.0.get() as *mu
 error: deadlock: the evaluated program deadlocked
   --> RUSTLIB/std/src/sys/pal/PLATFORM/thread.rs:LL:CC
    |
-LL |             let ret = libc::pthread_join(self.id, ptr::null_mut());
+LL |         let ret = unsafe { libc::pthread_join(id, ptr::null_mut()) };
    |                                                                  ^ the evaluated program deadlocked
    |
    = note: BACKTRACE:

tests/fail-dep/concurrency/libc_pthread_rwlock_write_write_deadlock.stderr

@@ -10,7 +10,7 @@ LL |             assert_eq!(libc::pthread_rwlock_wrlock(lock_copy.0.get() as *mu
 error: deadlock: the evaluated program deadlocked
   --> RUSTLIB/std/src/sys/pal/PLATFORM/thread.rs:LL:CC
    |
-LL |             let ret = libc::pthread_join(self.id, ptr::null_mut());
+LL |         let ret = unsafe { libc::pthread_join(id, ptr::null_mut()) };
    |                                                                  ^ the evaluated program deadlocked
    |
    = note: BACKTRACE: