Revert "test_cp: On MacOS, ignore tests that use /dev/fd/0"

This reverts commit 8e55c4a.

Author: drinkcat

tests/by-util/test_cp.rs

@@ -6322,7 +6322,6 @@ fn test_cp_archive_preserves_directory_permissions() {
 
 #[test]
 #[cfg(unix)]
-#[cfg_attr(target_os = "macos", ignore)] // Flaky on MacOS, see #8453
 fn test_cp_from_stdin() {
     let (at, mut ucmd) = at_and_ucmd!();
     let target = "target";
@@ -6390,7 +6389,6 @@ fn test_cp_update_none_interactive_prompt_no() {
 
 /// only unix has `/dev/fd/0`
 #[cfg(unix)]
-#[cfg_attr(target_os = "macos", ignore)] // Flaky on MacOS, see #8453
 #[test]
 fn test_cp_from_stream() {
     let target = "target";
@@ -6417,7 +6415,6 @@ fn test_cp_from_stream() {
 
 /// only unix has `/dev/fd/0`
 #[cfg(unix)]
-#[cfg_attr(target_os = "macos", ignore)] // Flaky on MacOS, see #8453
 #[test]
 fn test_cp_from_stream_permission() {
     let target = "target";