Add support for WASM backend #3149

Job	Run time
cabal	59s
cabal-doExactConfig	1m 47s
docs	3m 58s
build-extra-hackages	1m 45s
hix	1m 23s
hydra-ifdLevel-0-and-1	5m 33s
maintainer-scripts	42s
multi-target	2m 11s
nix-build	4m 13s
plan-extra-hackages	9s
runghc	8s
shellFor-hoogle	26s
shellFor-multiple-package	21s
shellFor-not-depends	31s
shellFor-single-package	32s
tests-benchmarks	18s
unit-tests	6s
check-materialization-concurrency	20s
check-path-support	15s
closure-size	6s
haskell-nix-roots-do-not-require-IFDs	35s
hix-cabal	16s
hydra-ifdLevel-2	11m 42s
hydra-ifdLevel-3	30m 11s
hydra-without-remote-builders-ghc9102	5m 41s
hydra-without-remote-builders-ghc967	4m 34s
nix-tools	15s
update-docs	5s
	1h 19m 2s

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