[REG 5.11->5.12] "qtquickcontrolsplugin" not found in static builds

Trying to  run an ios app using Quick Controls 1 results in:

QQmlApplicationEngine failed to load component[+qrc:/main.qml:9+] Type ApplicationWindow unavailable[+qrc:/Material/ApplicationWindow.qml:49+] Type Controls.ApplicationWindow unavailablefile::/qt-project.org/imports/QtQuick/Controls/qmldir:-1 module ":.qt-project.imports.QtQuick.Controls" plugin "qtquickcontrolsplugin" not found

This affects all 5.12.x versions up to 5.12.4 and 5.13.0. Qt 5.11.3 on the other hand does work.  Building an starting appdemo.pro on an ios device works fine on 5.11.3 and results in the above error on higher qt versions.

The ios builds are static and it seems that qtquickcontrolsplugin isn't included.

Attached is a short testcase. It might be related to addImportPath(...).

Update: The error isn't specific to ios, but also happens with qt for macos when trying to load a plugin with qml in a static build (and will likely happen on other platforms, too)