Add better support for armv7a cross compilation #2961

Job	Run time
nix-build	51s
cabal	16s
runghc	11s
unit-tests	10s
build-extra-hackages	10s
cabal-doExactConfig	12s
hix	31s
hydra-ifdLevel-0-and-1	5m 56s
maintainer-scripts	12s
plan-extra-hackages	10s
shellFor-hoogle	19s
shellFor-multiple-package	27s
multi-target	45s
shellFor-not-depends	27s
tests-benchmarks	11s
shellFor-single-package	27s
check-materialization-concurrency	22s
check-path-support	8s
closure-size	5s
docs	34s
haskell-nix-roots-do-not-require-IFDs	18s
hix-cabal	10s
hydra-ifdLevel-2	6m 27s
hydra-ifdLevel-3	30m 10s
hydra-without-remote-builders-ghc9101	7m 49s
hydra-without-remote-builders-ghc966	58s
nix-tools	24s
update-docs	6s
	58m 46s

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