Fix #2365 missing pg_config #3109

Job	Run time
nix-build	6m 15s
runghc	8s
unit-tests	5s
cabal	25s
cabal-doExactConfig	12s
multi-target	29s
shellFor-hoogle	17s
shellFor-multiple-package	18s
shellFor-not-depends	21s
shellFor-single-package	17s
tests-benchmarks	12s
build-extra-hackages	10s
closure-size	2s
docs	9m 6s
hix	42s
hydra-ifdLevel-0-and-1	2m 46s
hydra-ifdLevel-2	2m 45s
hydra-ifdLevel-3	30m 14s
maintainer-scripts	6s
plan-extra-hackages	11s
update-docs	8s
check-materialization-concurrency	19s
check-path-support	9s
haskell-nix-roots-do-not-require-IFDs	14s
hix-cabal	3m 5s
hydra-without-remote-builders-ghc9102	59s
hydra-without-remote-builders-ghc967	1m 30s
nix-tools	44s
	1h 2m 9s

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