Connect engine , makes a lot of use of __WIN__ preprocessor constant
It should be replaced by the standard _WIN32 (always defined, on any Windows, including _WIN64, by any compiler see https://bugs.mysql.com/bug.php?id=20338 and
MDEV-25602 for more info.
The reason why it is not in the scope of
MDEV-25602 is that Connect is an external component, usually maintained outside of core MariaDB, and thus this change should in the "upstream" repository.
one easy way way to do such a replacement is
from a Linux bash.