Add GHC 9.12.1 #2847

Job	Run time
cabal-doExactConfig	8s
cabal	38s
build-extra-hackages	11s
check-materialization-concurrency	18s
check-path-support	14s
closure-size	7s
docs	18s
haskell-nix-roots-do-not-require-IFDs	8s
hix-cabal	9s
hix	6m 48s
hydra-ifdLevel-0-and-1	3m 10s
hydra-ifdLevel-2	3m 8s
hydra-ifdLevel-3	9m 42s
hydra-without-remote-builders-ghc8107	1m 30s
hydra-without-remote-builders-ghc9101	37s
maintainer-scripts	10s
multi-target	33s
nix-build	17m 29s
nix-tools	23s
plan-extra-hackages	11s
runghc	15s
shellFor-hoogle	23s
shellFor-not-depends	13s
shellFor-multiple-package	23s
shellFor-single-package	28s
tests-benchmarks	8s
unit-tests	12s
update-docs	4s
	47m 58s

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