Make `ioHasBufFS` more general #217

Job	Run time
cabal-fmt (9.6.4, 3.10.3.0, ubuntu-latest)	3m 16s
cabal-check (9.6.4, 3.10.3.0, ubuntu-latest)	2m 20s
stylish-haskell (9.6.4, 3.10.3.0, ubuntu-latest)	11m 44s
build (8.10.7, 3.10.3.0, ubuntu-latest)	1m 23s
build (8.10.7, 3.10.3.0, windows-latest)	3m 10s
build (8.10.7, 3.10.3.0, macOS-latest)	2m 25s
build (9.2.8, 3.10.3.0, ubuntu-latest)	2m 26s
build (9.2.8, 3.10.3.0, windows-latest)	3m 27s
build (9.2.8, 3.10.3.0, macOS-latest)	2m 15s
build (9.4.8, 3.10.3.0, ubuntu-latest)	2m 0s
build (9.4.8, 3.10.3.0, windows-latest)	1m 9s
build (9.4.8, 3.10.3.0, macOS-latest)	4m 19s
build (9.6.4, 3.10.3.0, ubuntu-latest)	3m 7s
build (9.6.4, 3.10.3.0, windows-latest)	3m 28s
build (9.6.4, 3.10.3.0, macOS-latest)	3m 11s
build (9.8.2, 3.10.3.0, ubuntu-latest)	30s
build (9.8.2, 3.10.3.0, windows-latest)	1m 18s
build (9.8.2, 3.10.3.0, macOS-latest)	7m 56s
	59m 24s

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