find: make `InodeMatcher` & `LinksMatcher` unix-only #1015

Job	Run time
cargo clippy -- -D warnings	33s
cargo check (ubuntu-latest)	36s
cargo check (macOS-latest)	17s
cargo check (windows-latest)	1m 40s
Code coverage (ubuntu-latest, nightly, --all-features)	2m 2s
cargo fmt --all -- --check	14s
cargo test (ubuntu-latest)	30s
cargo test (macOS-latest)	32s
cargo test (windows-latest)	2m 29s
	8m 53s

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