add a TrivialClone implementation when deriving both Clone and Copy

Author: joboet

core/src/clone.rs

@@ -280,7 +280,7 @@ pub const unsafe trait TrivialClone: [const] Clone {}
 /// Derive macro generating an impl of the trait `Clone`.
 #[rustc_builtin_macro]
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
-#[allow_internal_unstable(core_intrinsics, derive_clone_copy)]
+#[allow_internal_unstable(core_intrinsics, derive_clone_copy, trivial_clone)]
 pub macro Clone($item:item) {
     /* compiler built-in */
 }