cp: don't open FIFOs/devices when preserving timestamps

[sylvestre]

set_file_times opens the destination before calling futimens; opening a FIFO with no writer blocks forever. Use the path-based utimensat variant for symlinks and other non-regular files.

Should make test tests/cp/preserve-mode.sh pass

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/cp/preserve-mode is no longer failing!
Congrats! The gnu test tests/misc/selinux is no longer failing!
Congrats! The gnu test tests/expand/bounded-memory is now passing!
Congrats! The gnu test tests/rm/many-dir-entries-vs-OOM is now passing!

[codspeed-hq]

Merging this PR will not alter performance

✅ 339 untouched benchmarks
⏩ 46 skipped benchmarks¹

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_{Comparing sylvestre:cp-preserve-mode (accfde5) with main (ef50d8b)}

Footnotes

1. 46 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[sylvestre]

Congrats! The gnu test tests/cp/preserve-mode is no longer failing!

!
automerge then