Bug 1789505 - Silence rustc 1.65 warning about mem::uninitialized. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D156768

third_party/rust/mio-0.6.23/src/sys/unix/uds.rs

@@ -50,6 +50,8 @@ unsafe fn sockaddr_un(path: &Path)
 }
 
 fn sun_path_offset() -> usize {
+    // Silence rustc 1.65 warning about mem::uninitialized.
+    #[allow(invalid_value)]
     unsafe {
         // Work with an actual instance of the type since using a null pointer is UB
         let addr: libc::sockaddr_un = mem::uninitialized();