test_mkfifo_permission_unchanged_when_failed intermittent failure

    running 1 test
    bin: "/home/runner/work/coreutils/coreutils/target/debug/coreutils"
    write(default): /tmp/.tmpzfXtl5/test_file
    run: /home/runner/work/coreutils/coreutils/target/debug/coreutils mkfifo test_file -m 666
    test test_mkfifo::test_mkfifo_permission_unchanged_when_failed ... FAILED

    failures:

    ---- test_mkfifo::test_mkfifo_permission_unchanged_when_failed stdout ----
    ---- test_mkfifo::test_mkfifo_permission_unchanged_when_failed stderr ----


    failures:
        test_mkfifo::test_mkfifo_permission_unchanged_when_failed

    test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 5169 filtered out; finished in 0.14s
    
  stderr ───

    thread 'main' (42252) panicked at tests/by-util/test_mkfifo.rs:236:10:
    assertion failed: `(left == right)`

    Diff < left / right > :
     mkfifo: cannot create fifo 'test_file': File exists
    <LLVM Profile Error: Failed to write file "/home/runner/work/coreutils/coreutils/coverage/traces/coverage-10764279602708793238_3.profraw": Permission denied

https://github.com/uutils/coreutils/actions/runs/24202125863/job/70648306358

Start with tests/by-util/test_mkfifo.rs at line 236 and reproduce test_mkfifo::test_mkfifo_permission_unchanged_when_failed using the mkfifo command shown in the log. Compare the intermittent failure with the linked GitHub Actions run, including the LLVM Profile Error, and confirm the test completes reliably with the expected failure output.