https://github.com/som-snytt/scala/tree/issue/7775-sysprop-CME

I don't know why it didn't use my commit message... This is for visibility in case it's useful. It was fun just reading the code.

    Just when you want to iterate over system properties in search
    of a setting, someone else wants to configure their module by
    setting a property.
    
    Avoid ConcurrentModificationExceptions by iterating over property
    names only, which are not backed by the underlying map.