example engine is packaged on windows

KB says that the example engine "is no longer included in MariaDB". And, indeed, on linux it is not, because release binaries are configured with

cmake -DBUILD_CONFIG=mysql_release

But on Windows we apparently don't do that and ha_example.dll is distributed too. This is inconsistent.

actually, I think that example engine should be included. we package other test plugins, why not this one?