Build hadrian with ghc 9.6.6 if available. (#2342) #3031

Job	Run time
cabal-doExactConfig	44s
cabal	43s
build-extra-hackages	46s
check-materialization-concurrency	20s
check-path-support	36s
closure-size	6s
docs	10m 41s
haskell-nix-roots-do-not-require-IFDs	1m 48s
hix	4m 0s
hix-cabal	4m 57s
hydra-ifdLevel-0-and-1	7m 54s
hydra-ifdLevel-2	20m 15s
hydra-ifdLevel-3	30m 15s
hydra-without-remote-builders-ghc9101	3m 55s
hydra-without-remote-builders-ghc966	3m 4s
maintainer-scripts	9s
multi-target	1m 10s
nix-build	5m 16s
plan-extra-hackages	29s
nix-tools	1m 45s
runghc	9s
shellFor-hoogle	49s
shellFor-multiple-package	23s
shellFor-not-depends	57s
shellFor-single-package	3m 3s
tests-benchmarks	38s
unit-tests	9s
update-docs	5s
	1h 45m 6s

Provide feedback