Creating QSslSocket when schannel is in use takes too long time

A simple reproducer:

QElapsedTimer timer;
timer.start();

QSslSocket s;

qDebug() << timer.elapsed();

According to the original reporter, timer reports ~500ms and the reason is the fact that

QWinTimeZonePrivate::availableTimeZoneIds()

is being called ~5000 times.

There has been a patch here:
https://codereview.qt-project.org/c/qt/qtbase/+/518217
The original reporter tested it, and reported back that the patch only fixes release build of application. The debug build still suffers from long instantiation time.

On the other hand, OpenSSL seems to work fine. And it can be a schannel issue.