Add GHC 9.12.1 (#2302) #2853

Job	Run time
cabal-doExactConfig	13s
cabal	10s
build-extra-hackages	7s
check-materialization-concurrency	20s
check-path-support	7s
closure-size	3s
docs	38s
haskell-nix-roots-do-not-require-IFDs	12s
hix-cabal	14s
hix	31s
hydra-ifdLevel-0-and-1	3m 47s
hydra-ifdLevel-2	2m 56s
hydra-without-remote-builders-ghc8107	31s
hydra-without-remote-builders-ghc9101	1m 53s
hydra-ifdLevel-3	28m 39s
maintainer-scripts	12s
multi-target	30s
nix-build	15m 48s
nix-tools	16s
plan-extra-hackages	5s
runghc	11s
shellFor-hoogle	7s
shellFor-multiple-package	10s
shellFor-not-depends	20s
shellFor-single-package	14s
tests-benchmarks	10s
unit-tests	6s
update-docs	4s
	58m 34s

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