Apply deny(unsafe_op_in_unsafe_fn) to all of sys/unsupported.

library/std/src/sys/unsupported/common.rs

@@ -39,10 +39,13 @@ pub fn hashmap_random_keys() -> (u64, u64) {
 pub enum Void {}
 
 pub unsafe fn strlen(mut s: *const c_char) -> usize {
-    let mut n = 0;
-    while *s != 0 {
-        n += 1;
-        s = s.offset(1);
+    // SAFETY: The caller must guarantee `s` points to a valid 0-terminated string.
+    unsafe {
+        let mut n = 0;
+        while *s != 0 {
+            n += 1;
+            s = s.offset(1);
+        }
+        n
     }
-    return n;
 }

library/std/src/sys/unsupported/mod.rs

@@ -1,3 +1,5 @@
+#![deny(unsafe_op_in_unsafe_fn)]
+
 pub mod alloc;
 pub mod args;
 pub mod cmath;

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

@@ -1,5 +1,3 @@
-#![deny(unsafe_op_in_unsafe_fn)]
-
 use crate::cell::Cell;
 
 pub struct Mutex {

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

@@ -1,5 +1,3 @@
-#![deny(unsafe_op_in_unsafe_fn)]
-
 use crate::cell::Cell;
 
 pub struct RWLock {