tail: disable clippy::assigning_clones on OpenBSD

- Avoid error on OpenBSD stable/7.5 with clippy (lint)
- assigning_clones added in Rust 1.78.0 (1.76 used on OpenBSD 7.5)
https://rust-lang.github.io/rust-clippy/master/index.html#/assigning_clones

Signed-off-by: Laurent Cheylus <foxy@free.fr>

src/uu/tail/src/follow/watch.rs

@@ -45,7 +45,9 @@ impl WatcherRx {
             Tested for notify::InotifyWatcher and for notify::PollWatcher.
             */
             if let Some(parent) = path.parent() {
-                #[allow(clippy::assigning_clones)]
+                // clippy::assigning_clones added with Rust 1.78
+                // Rust version = 1.76 on OpenBSD stable/7.5
+                #[cfg_attr(not(target_os = "openbsd"), allow(clippy::assigning_clones))]
                 if parent.is_dir() {
                     path = parent.to_owned();
                 } else {