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-jit crate, which contains JIT-based execution
for wasm, using the wasm ABI defined by wasmtime-environ and the
runtime support provided by wasmtime-runtime.