Build issue with private headers

Some Qt plugins in webOS are being built with qmake. They have been using private modules by referring to the related pri file in its pro file.
But we realized that module pri files generated in Qt 6 has incorrect include paths - it exposes public headers only not private headers. It results in build errors due to headers not found.

Here is a suggested fix for that issue, just submitted to Qt gerrit. I would like Qt team to review it.

https://codereview.qt-project.org/c/qt/qtbase/+/329311

It is also applied to our internal engineering build to address related build issues.