Generate dummy-ghc from raw ghc source #2062

Job	Run time
unit-tests	15s
cabal	33s
cabal-doExactConfig	23s
nix-build	24s
runghc	31s
shellFor-multiple-package	46s
multi-target	59s
shellFor-single-package	52s
tests-benchmarks	12s
build-extra-hackages	19s
docs	50s
hix	1m 20s
hydra-ifdLevel-0-and-1	1m 27s
hydra-ifdLevel-2	19s
hydra-ifdLevel-3-and-ghc-8-10	13s
maintainer-scripts	8s
plan-extra-hackages	21s
shellFor-hoogle	18s
shellFor-not-depends	14s
check-materialization-concurrency	19s
check-path-support	22s
closure-size	8s
haskell-nix-roots-do-not-require-IFDs	6s
hix-cabal	15s
hydra-ifdLevel-3-and-ghc-9-2	44s
hydra-ifdLevel-3-and-not-ghc-8-10-or-9-2	12s
hydra-without-remote-builders	16s
nix-tools	13s
update-docs	12s
	13m 11s

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