Attempting to freeze the module namespace exotic object should not affect the `writable`-ity of the properties as that exercises the same `DefineOwnProperty` operation according to [`SetIntegrityLevel`](https://tc39.es/ecma262/#sec-setintegritylevel).
@erights discovered a [bug in v8](https://bugs.chromium.org/p/v8/issues/detail?id=12240) where, while the `Object.freeze` operation throws, it actually makes exported properties non-writable one by one.
At the request of @syg, I'm contributing a test against this behavior. The bug in v8 actually leads to a breakage of the objects invariants, however I'm not testing for that here as the root cause is the illegal freezing of the export.