uucore: support cygwin #14127

Job	Run time
Style/spelling (ubuntu-latest, feat_os_unix)	17s
Style/lint (windows-latest, feat_os_windows)	2m 18s
Style/format (ubuntu-latest, feat_os_unix)	9s
Style/toml	12s
Style/lint (ubuntu-latest, all, true)	1m 20s
Style/lint (macos-latest, feat_os_macos)	1m 17s
Style/Python	6s
Pre-commit hooks	21s
	6m 0s

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