Static builds of QT seem ok, but own projects get error when configured

Sources are obtained from https://download.qt.io/archive/qt/...

After unpacking the tarfile (as root, in /usr/local/src) I do the usual:

cd <qt_everywhere-src-xxx>
mkdir build-static
cd build-static

../configure -static -prefix /usr/local/qt-6.8.2-static

cmake --build . --parallel

cmake --install .

All seems to go well. However, when I then want to cmake-configure my own project I get errors: HARFBUFF_INCLUDE_DIR not fuond, Qt6GUi set no not found (see attachement)

When I build the shared version of Qt (same procedure) I experience no problems.

I have experienced in the past similar problems, which I could solve by setting ownership and permission correctly. In the attachment "README_BUILD_STATIC.bwvb" you can find a note I once made on this. However, this no longer solves the issue.

In short, the static build of Qt -which I use to deploy my application, is no longer useable. Upgrading to 6.9.0 did not solve the issue.