cp: 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/cp/src/cp.rs

@@ -1120,7 +1120,9 @@ fn parse_path_args(
     };
 
     if options.strip_trailing_slashes {
-        #[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))]
         for source in &mut paths {
             *source = source.components().as_path().to_owned();
         }