Add support for WASM backend #3243

Job	Run time
runghc	12s
nix-build	4m 23s
unit-tests	10s
cabal	1m 12s
hydra-ifdLevel-0-and-1	2m 52s
shellFor-hoogle	1m 18s
docs	4m 29s
maintainer-scripts	8s
hydra-ifdLevel-3	30m 18s
shellFor-single-package	1m 28s
tests-benchmarks	14s
cabal-doExactConfig	17s
shellFor-multiple-package	30s
build-extra-hackages	14s
shellFor-not-depends	1m 26s
closure-size	7s
hix	1m 21s
plan-extra-hackages	10s
hydra-ifdLevel-2	10m 22s
multi-target	2m 9s
update-docs	8s
check-path-support	17s
check-materialization-concurrency	23s
check-nix-tools	17s
hydra-without-remote-builders-ghc9102	2m 7s
haskell-nix-roots-do-not-require-IFDs	19s
hix-cabal	15s
hydra-without-remote-builders-ghc967	2m 6s
	1h 9m 12s

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