Add support for WASM backend #3329

Job	Run time
nix-build	31s
runghc	26s
cabal-doExactConfig	3m 9s
unit-tests	13s
multi-target	15s
shellFor-multiple-package	11m 56s
maintainer-scripts	37s
cabal	16s
shellFor-not-depends	21s
hix	1h 7m 5s
shellFor-single-package	13m 6s
shellFor-hoogle	16s
build-extra-hackages	16s
plan-extra-hackages	14s
closure-size	9s
docs	19m 16s
tests-benchmarks	18s
check-nix-tools	23s
check-path-support	14s
hydra-ifdLevel-0-and-1	5m 18s
hydra-without-remote-builders-ghc9102	17s
check-materialization-concurrency	26s
haskell-nix-roots-do-not-require-IFDs	31s
update-docs	11s
hix-cabal	19s
hydra-ifdLevel-3	30m 18s
hydra-ifdLevel-2	7m 22s
hydra-without-remote-builders-ghc967	4m 56s
	2h 48m 39s

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