Add support for WASM backend #3346

Job	Run time
unit-tests	50s
nix-build	9m 7s
runghc	1m 15s
cabal	1m 19s
build-extra-hackages	2m 34s
shellFor-hoogle	1m 9s
hydra-ifdLevel-2	20m 18s
shellFor-multiple-package	16s
update-docs	13s
check-materialization-concurrency	26s
tests-benchmarks	17s
hix	1h 23m 5s
cabal-doExactConfig	15s
multi-target	20s
docs	3h 10m 53s
shellFor-single-package	16s
hydra-ifdLevel-3	30m 19s
hydra-ifdLevel-0-and-1	20m 16s
closure-size	11s
maintainer-scripts	15s
plan-extra-hackages	14s
shellFor-not-depends	19s
hydra-without-remote-builders-ghc9102	1m 8s
check-path-support	8m 6s
haskell-nix-roots-do-not-require-IFDs	1m 37s
hydra-without-remote-builders-ghc967	32s
hix-cabal	10m 54s
check-nix-tools	2h 18m 55s
	8h 45m 19s

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