awkward structure in mjs build

mjs module looks like:

```js
var Module = (() => {
var _scriptDir = import.meta.url;

return (
async function(Module = {}) {
var Module = typeof Module != "undefined" ? Module : {};

// module stuff
}
);
})();

export default Module;
```

There are a few problems with this:
- Safari doesn't understands this and I truly believe the cause is a Safari bug (tested under Safari 16.4 MacOS / iOS)
- Default argument value assumes that argument is defined
- Hoisting doesn't work here, es module provides module scope

You could really name things better. The first Module actually is a factory that generates a Module, the second one is Module closure and the third one is the Module, which is the factory result.