cksum: improve performance (Closes: #8573) #10657

Job	Run time
Style/spelling (ubuntu-latest, feat_os_unix)	3m 4s
Style/lint (ubuntu-latest, all, true)	1m 10s
Pre-commit hooks	19s
Style/Python	7s
Style/toml	17s
Style/lint (macos-latest, feat_os_macos)	1m 5s
Style/lint (windows-latest, feat_os_windows)	2m 0s
Style/format (ubuntu-latest, feat_os_unix)	16s
	8m 18s

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