CI: Cache wasm target directory. #658

Job	Run time
deny	43s
deny	47s
build (ubuntu, stable, locked, true)	24m 34s
build (ubuntu, stable, locked, true)	9m 27s
lint (stable)	7m 44s
lint (stable)	3m 22s
incremental-mutants	0s
incremental-mutants	0s
build (windows, stable, locked, false)	40m 51s
build (windows, stable, locked, false)	18m 35s
lint (nightly)	5m 42s
lint (nightly)	2m 12s
miri	1m 36s
miri	1m 38s
build (macos, stable, locked, false)	18m 51s
build (macos, stable, locked, false)	9m 21s
lint (beta)	5m 41s
lint (beta)	1m 45s
build (ubuntu, nightly, locked, false)	22m 59s
build (ubuntu, nightly, locked, false)	9m 19s
no_std	36s
no_std	34s
build (ubuntu, beta, locked, false)	22m 53s
build (ubuntu, beta, locked, false)	10m 41s
build (ubuntu, stable, latest, false)	24m 51s
build (ubuntu, stable, latest, false)	10m 35s
build (ubuntu, stable, minimal, false)	21m 56s
build (ubuntu, stable, minimal, false)	10m 13s
fuzz	53s
fuzz	15m 33s
features	51s
features	27m 50s
deploy	0s
deploy	0s
	5h 32m 33s

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