qt-cmake-private installs to COIN installation path instead of local installation path

bin/qt-cmake-private can be used to configure additional modules to build against an installed Qt.

When using qt-cmake-private from 6.0 from the online installer, to configure and build a module (in my case qt5compat, since that is not part of the online install), it configures and builds fine.

When doing "cmake --install .", though, it tries to install the module into "/Users/qt/work/install/" which is of course wrong for my Qt installation.