Prior to this change, for an example compiler error test case with
multiple identical errors messages such as

```
:1:2: error: foo
:1:2: error: foo
```

the test harness would never increment the error index thus only
marking the very first error message as handled yielding a false
positive.

Additionally, while here, regress `dereference_anyopaque` test case
as not passing on `wasm32-wasi` target.