Add GHC 9.12.1 #2841

Job	Run time
cabal-doExactConfig	4m 8s
cabal	4m 8s
nix-build	8m 54s
runghc	4m 9s
unit-tests	8s
multi-target	8m 58s
shellFor-hoogle	8m 42s
shellFor-multiple-package	8m 35s
shellFor-single-package	6m 6s
tests-benchmarks	11s
build-extra-hackages	1m 19s
check-materialization-concurrency	20s
check-path-support	1m 4s
closure-size	4s
docs	1m 49s
haskell-nix-roots-do-not-require-IFDs	1m 36s
hix	5m 7s
hix-cabal	1m 46s
hydra-ifdLevel-0-and-1	11m 11s
hydra-ifdLevel-2	5m 28s
hydra-without-remote-builders-ghc8107	57s
hydra-ifdLevel-3	5m 9s
hydra-without-remote-builders-ghc9101	54s
maintainer-scripts	7s
nix-tools	12s
plan-extra-hackages	5s
shellFor-not-depends	14s
update-docs	7s
	1h 31m 28s

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