Rollup merge of rust-lang#66350 - hermitcore:hermit, r=rkruppe

protect creation of destructors by a mutex

- add on HermitCore an additional lock to protect static data

src/libstd/sys/hermit/thread_local.rs

@@ -3,6 +3,7 @@
 use crate::collections::BTreeMap;
 use crate::ptr;
 use crate::sync::atomic::{AtomicUsize, Ordering};
+use crate::sys_common::mutex::Mutex;
 
 pub type Key = usize;
 
@@ -11,6 +12,7 @@ type Dtor = unsafe extern fn(*mut u8);
 static NEXT_KEY: AtomicUsize = AtomicUsize::new(0);
 
 static mut KEYS: *mut BTreeMap<Key, Option<Dtor>> = ptr::null_mut();
+static KEYS_LOCK: Mutex = Mutex::new();
 
 #[thread_local]
 static mut LOCALS: *mut BTreeMap<Key, *mut u8> = ptr::null_mut();
@@ -32,6 +34,7 @@ unsafe fn locals() -> &'static mut BTreeMap<Key, *mut u8> {
 #[inline]
 pub unsafe fn create(dtor: Option<Dtor>) -> Key {
     let key = NEXT_KEY.fetch_add(1, Ordering::SeqCst);
+    let _guard = KEYS_LOCK.lock();
     keys().insert(key, dtor);
     key
 }