Add support for WASM backend #3322

Job	Run time
unit-tests	19s
runghc	42s
cabal-doExactConfig	40s
nix-build	45s
cabal	14s
tests-benchmarks	49s
check-materialization-concurrency	24s
hydra-ifdLevel-2	20m 19s
build-extra-hackages	1m 55s
closure-size	17s
haskell-nix-roots-do-not-require-IFDs	5m 32s
multi-target	17s
hydra-ifdLevel-0-and-1	16m 7s
shellFor-hoogle	14s
check-path-support	1m 0s
hydra-without-remote-builders-ghc967	2m 19s
shellFor-multiple-package	15s
hydra-ifdLevel-3	30m 18s
shellFor-not-depends	15s
hix	1h 24m 48s
shellFor-single-package	13s
maintainer-scripts	11s
docs	23m 42s
plan-extra-hackages	15s
update-docs	15s
hydra-without-remote-builders-ghc9102	26s
hix-cabal	13m 25s
check-nix-tools	5m 53s
	3h 31m 49s

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