Use unit id for package key #2518

Job	Run time
cabal-doExactConfig	2m 34s
cabal	2m 33s
nix-build	4m 54s
tests-benchmarks	1m 14s
unit-tests	13s
maintainer-scripts	22s
plan-extra-hackages	19s
multi-target	55s
shellFor-hoogle	39s
shellFor-multiple-package	39s
shellFor-single-package	22s
build-extra-hackages	15s
docs	1m 51s
hix	1m 31s
hydra-ifdLevel-0-and-1	56s
hydra-ifdLevel-2	41s
hydra-ifdLevel-3-and-ghc-8-10	25s
hydra-ifdLevel-3-and-ghc-9-2	20s
hydra-ifdLevel-3-and-not-ghc-8-10-or-9-2	19s
runghc	16s
check-materialization-concurrency	23s
check-path-support	13s
closure-size	7s
haskell-nix-roots-do-not-require-IFDs	8s
hix-cabal	2m 59s
hydra-without-remote-builders-ghc8107	2m 37s
hydra-without-remote-builders-ghc9101	2m 13s
nix-tools	1m 59s
shellFor-not-depends	20s
update-docs	8s
	32m 25s

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