As suggested [here](https://github.com/Amanieu/hashmap_core/pull/10#issuecomment-455866083). This also allows us to re-enable the basic compile fuzz target.
This is the wasmtime-runtime crate, which contains wasm runtime library
support, supporting the wasm ABI used by wasmtime-environ,
wasmtime-jit, and wasmtime-obj.
This crate does not make a host vs. target distinction; it is meant to be compiled for the target.