Add better support for armv7a cross compilation #2625

Job	Run time
nix-build	41s
runghc	24s
cabal-doExactConfig	25s
build-extra-hackages	6s
cabal	13s
hix	26s
maintainer-scripts	7s
multi-target	28s
plan-extra-hackages	4s
shellFor-hoogle	7s
shellFor-multiple-package	11s
shellFor-not-depends	12s
shellFor-single-package	14s
tests-benchmarks	8s
unit-tests	5s
check-materialization-concurrency	24s
check-path-support	5s
docs	19s
closure-size	3s
haskell-nix-roots-do-not-require-IFDs	4s
hix-cabal	5s
hydra-ifdLevel-0-and-1	2m 20s
hydra-ifdLevel-2	3m 2s
hydra-ifdLevel-3	9m 9s
hydra-without-remote-builders-ghc8107	6s
hydra-without-remote-builders-ghc9101	2s
nix-tools	9s
update-docs	4s
	19m 43s

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