Build

replace `nix-shell` with Nix Flake #581

Job	Run time
continuous-integration (8.10.7)	1m 59s
continuous-integration (9.0.2)	1m 52s
continuous-integration (9.2.8)	1m 29s
continuous-integration (9.4.5)	2m 29s
continuous-integration (9.6.4)	11m 59s
continuous-integration (9.8.2)	11m 50s
continuous-integration (9.10.1)	1m 27s
continuous-integration (9.12.1, --allow-newer=base --allow-newer=template-haskell --allow-newer=g...	12m 15s
	45m 20s

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