Add better support for armv7a cross compilation #2819

Job	Run time
cabal	10s
cabal-doExactConfig	15s
build-extra-hackages	6s
check-path-support	6s
closure-size	4s
check-materialization-concurrency	23s
docs	20s
haskell-nix-roots-do-not-require-IFDs	16s
hix	26s
hix-cabal	9s
hydra-ifdLevel-0-and-1	7m 17s
hydra-ifdLevel-2	3m 58s
hydra-ifdLevel-3	3m 15s
hydra-without-remote-builders-ghc8107	7s
hydra-without-remote-builders-ghc9101	7s
maintainer-scripts	8s
multi-target	34s
nix-build	27s
nix-tools	10s
plan-extra-hackages	6s
runghc	7s
shellFor-hoogle	9s
shellFor-multiple-package	13s
shellFor-not-depends	16s
shellFor-single-package	16s
tests-benchmarks	6s
unit-tests	5s
update-docs	5s
	19m 41s

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