Move WASM compile steps to service/test time.

This will hopefully eliminate, once and for all, our issues with corrupted WASM binaries. WASM binary "corruption" probably has to do with compilation and execution taking place on different machines (and so supervenes on OS differences, or architecture differences, or endianness, or something). By moving these steps to run just before the test/serve command, we ensure that they are executed on the same machine that will be invoking the binaries.