Specifying `unsafe` causes hang/freeze

I have a project where as soon as I specify `unsafe: true`, the compilation hangs forever.

My config:

```js
terserOptions: {,
  compress: {
    unsafe: true
  }
}
```

I figured this might be related to doing multiple passes, so I tried adding `passes: 1`, but the hang still occurs.

Any suggestions of other things I could try before I go digging in the `terser` code? :)