feat: readOnlyRootFilesystem can`t be used

Hi,

I have this issue.

I set `readOnlyRootFilesystem: true`

When I start the container I get:

```
/opt/app-root/etc/generate_container_user: line 10: /opt/app-root/etc/passwd: Read-only file system
```

I would like to use an empty dir to store /opt/app-root/etc/passwd contents. But this seesm not possible since /opt/app-root/etc/generate_container_user is in the same folder.