test_follow_name_truncate4 is intermittent

[sylvestre]

Found in:
https://github.com/uutils/coreutils/runs/6827401685?check_suite_focus=true

---- test_tail::test_follow_name_truncate4 stdout ----
current_directory_resolved: 
write(append): /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/.tmpxBKdqN/file
run: /Users/runner/work/coreutils/coreutils/target/debug/coreutils tail -s.1 --max-unchanged-stats=1 -F file
write(truncate): /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/.tmpxBKdqN/file
remove: "/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/.tmpxBKdqN/file"
write(append): /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/.tmpxBKdqN/file
run: /Users/runner/work/coreutils/coreutils/target/debug/coreutils tail -s.1 --max-unchanged-stats=1 -F file ---disable-inotify
write(truncate): /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/.tmpxBKdqN/file
thread 'test_tail::test_follow_name_truncate4' panicked at 'assertion failed: buf_stderr.is_empty()', /Users/runner/work/coreutils/coreutils/tests/by-util/test_tail.rs:1755:9

cc @jhscheer