Guide the user to using `#[crate_type="cdylib"]` when using Wasm. #715

Job	Run time
Build frontend	2m 9s
Build stable compiler container	5m 5s
Build beta compiler container	4m 55s
Build nightly compiler container	4m 53s
Build backend	3m 8s
Build clippy tool container	3m 0s
Build miri tool container	4m 32s
Build rustfmt tool container	47s
Running integration tests	10m 12s
Release artifacts	0s
	38m 41s

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