Based on https://store.kde.org/p/1081013/, updated and working for Qt 6.6.2 & KDE Frameworks 6.0.0.
This lines will install it correctly for Arch Linux, be careful with other distros!
cmake -B build -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_INSTALL_LIBDIR=lib
make -C build
sudo make -C build install