Add support for WASM backend #3069

Job	Run time
cabal	34s
cabal-doExactConfig	32s
build-extra-hackages	28s
check-path-support	7s
check-materialization-concurrency	24s
closure-size	3s
docs	1m 11s
hix	1m 6s
haskell-nix-roots-do-not-require-IFDs	13s
hix-cabal	13s
hydra-ifdLevel-0-and-1	3m 14s
hydra-ifdLevel-2	5m 5s
hydra-ifdLevel-3	30m 11s
hydra-without-remote-builders-ghc9101	54s
hydra-without-remote-builders-ghc967	3m 22s
maintainer-scripts	7s
multi-target	52s
nix-build	4m 20s
nix-tools	17s
plan-extra-hackages	6s
runghc	9s
shellFor-hoogle	16s
shellFor-multiple-package	17s
shellFor-not-depends	24s
shellFor-single-package	23s
tests-benchmarks	9s
unit-tests	6s
update-docs	5s
	55m 8s

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