Safari on iOS: Assertion failed: no binaryen method succeeded.

On trying to load the library in Safari on iOS 11, you get 2 errors:

```js
Assertion failed: no binaryen method succeeded.
```

and

```js
abort("Assertion failed: no binaryen method succeeded."). Build with -s ASSERTIONS=1 for more info.
```

Which results in OpenCV failing to load  and causing a 

```
ReferenceError: Can't find variable: cv
```

error.