Add support for WASM backend #3343

Job	Run time
cabal-doExactConfig	4m 8s
unit-tests	17s
nix-build	31m 9s
shellFor-single-package	11m 0s
shellFor-multiple-package	10m 47s
runghc	1m 58s
plan-extra-hackages	1m 4s
shellFor-not-depends	1m 55s
cabal	4m 7s
maintainer-scripts	10s
tests-benchmarks	25s
multi-target	9m 22s
build-extra-hackages	23s
shellFor-hoogle	8m 18s
check-nix-tools	26s
hix-cabal	38s
hydra-ifdLevel-0-and-1	10m 0s
docs	3h 19m 3s
hix	8m 53s
hydra-ifdLevel-2	17m 13s
hydra-without-remote-builders-ghc9102	9m 28s
hydra-without-remote-builders-ghc967	8m 52s
check-path-support	41s
hydra-ifdLevel-3	30m 17s
update-docs	11s
haskell-nix-roots-do-not-require-IFDs	1m 23s
closure-size	9s
check-materialization-concurrency	26s
	6h 12m 43s

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