chore: disable some unix-only helper functions on Windows #128

Job	Run time
build-windows-pr (x86_64-pc-windows-msvc, dev)	9m 36s
build-linux-pr (dev, x86_64-unknown-linux-gnu)	7m 59s
build-windows-pr (x86_64-pc-windows-msvc, release)	4m 51s
build-windows-master	0s
build-windows-stable	0s
build-linux-pr (dev, armv7-unknown-linux-gnueabihf)	1m 12s
build-linux-pr (dev, aarch64-linux-android)	1m 15s
build-linux-pr (release, x86_64-unknown-linux-gnu)	3m 57s
build-linux-master	0s
build-linux-pr (release, armv7-unknown-linux-gnueabihf)	1m 58s
build-linux-stable	0s
build-freebsd	31m 22s
build-linux-pr (release, aarch64-linux-android)	2m 18s
build-macos (x86_64-apple-darwin, dev)	12m 15s
check	37s
build-macos (x86_64-apple-darwin, release)	3m 5s
build-all-features (x86_64-unknown-linux-gnu)	3m 21s
build-macos (aarch64-apple-darwin, dev)	1m 30s
build-macos (aarch64-apple-darwin, release)	3m 15s
doc	4s
conclusion	2s
	1h 28m 37s

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