Add support for WASM backend #3324

Job	Run time
unit-tests	24s
nix-build	21m 27s
build-extra-hackages	50s
runghc	1m 34s
cabal	2m 35s
tests-benchmarks	1m 23s
shellFor-single-package	6m 28s
plan-extra-hackages	15s
cabal-doExactConfig	17s
multi-target	5m 52s
shellFor-multiple-package	5m 15s
shellFor-hoogle	2m 27s
maintainer-scripts	10s
shellFor-not-depends	33s
hydra-ifdLevel-0-and-1	8m 36s
docs	12m 53s
hydra-ifdLevel-2	20m 18s
hix	47m 13s
closure-size	9s
update-docs	16s
hydra-without-remote-builders-ghc9102	3m 30s
check-materialization-concurrency	24s
hydra-ifdLevel-3	30m 17s
check-path-support	29s
hix-cabal	5m 27s
hydra-without-remote-builders-ghc967	1m 48s
haskell-nix-roots-do-not-require-IFDs	27s
check-nix-tools	1m 31s
	3h 2m 48s

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