Add support for WASM backend #3248

Job	Run time
runghc	1m 36s
cabal	1m 39s
nix-build	20m 6s
unit-tests	10s
hydra-ifdLevel-2	20m 18s
cabal-doExactConfig	1m 38s
tests-benchmarks	1m 56s
multi-target	49s
hix	5m 35s
shellFor-hoogle	3m 45s
docs	17m 42s
hydra-ifdLevel-3	30m 17s
hydra-ifdLevel-0-and-1	6m 30s
shellFor-not-depends	1m 55s
shellFor-single-package	33s
plan-extra-hackages	17s
shellFor-multiple-package	5m 16s
build-extra-hackages	17s
maintainer-scripts	16s
closure-size	17s
check-path-support	23s
check-nix-tools	2m 51s
hix-cabal	2m 33s
check-materialization-concurrency	25s
haskell-nix-roots-do-not-require-IFDs	35s
hydra-without-remote-builders-ghc9102	5m 43s
hydra-without-remote-builders-ghc967	4m 36s
update-docs	12s
	2h 18m 10s

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