Use ghcup-setup in CI #55

Job	Run time
darwin_arm (self-hosted, macOS, ARM64, 8.10.7)	1s
arm (arm32v7)	1s
darwin_arm (self-hosted, macOS, ARM64, 9.2.8)	1s
emulated (s390x)	27s
arm (arm64v8)	1s
darwin_arm (self-hosted, macOS, ARM64, 9.4.7)	1s
build (ubuntu-latest, 8.6, 3.8.1.0)	7s
emulated (ppc64le)	24s
build (ubuntu-latest, 8.8, 3.8.1.0)	7s
build (ubuntu-latest, 8.10, 3.8.1.0)	7s
freebsd (self-hosted, FreeBSD, X64, 9.4.8)	2m 15s
i386	3m 2s
build (ubuntu-latest, 9.0, 3.8.1.0)	7s
freebsd (self-hosted, FreeBSD, X64, 9.6.4)	3m 3s
build (ubuntu-latest, 9.2, 3.8.1.0)	7s
build (ubuntu-latest, 9.4, 3.8.1.0)	9s
build (ubuntu-latest, 9.6, 3.8.1.0)	7s
build (ubuntu-latest, 9.8, 3.8.1.0)	6s
build (macOS-12, 9.4, 3.8.1.0)	1s
build (macOS-12, 9.6, 3.8.1.0)	1s
build (windows-latest, 9.4, 3.8.1.0)	3m 0s
build (windows-latest, 9.6, 3.8.1.0)	3m 0s
	16m 15s

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