Add support for WASM backend #3342

Job	Run time
cabal	1m 9s
unit-tests	11s
runghc	7m 25s
nix-build	1m 20s
cabal-doExactConfig	1m 24s
docs	1m 0s
hydra-ifdLevel-2	20m 18s
tests-benchmarks	13s
update-docs	9s
hydra-ifdLevel-3	30m 18s
shellFor-single-package	31s
shellFor-multiple-package	23s
shellFor-hoogle	19s
maintainer-scripts	11s
closure-size	9s
check-materialization-concurrency	25s
hix	1h 8m 53s
multi-target	18s
hydra-ifdLevel-0-and-1	5m 6s
build-extra-hackages	1m 1s
shellFor-not-depends	32s
plan-extra-hackages	13s
haskell-nix-roots-do-not-require-IFDs	25s
hydra-without-remote-builders-ghc9102	3m 50s
hydra-without-remote-builders-ghc967	3m 50s
hix-cabal	8m 50s
check-nix-tools	25s
check-path-support	14s
	2h 39m 2s

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