Missing cmake dep?

[tsimonq2]

In file included from /<<PKGBUILDDIR>>/src/filedialoghelper.h:28,
                 from /<<PKGBUILDDIR>>/src/filedialoghelper.cpp:28:
/usr/include/libfm-qt/filedialoghelper.h:5:10: fatal error: qpa/qplatformdialoghelper.h: No such file or directory
    5 | #include <qpa/qplatformdialoghelper.h> // this private header is subject to changes
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
make[3]: *** [src/CMakeFiles/xdg-desktop-portal-lxqt.dir/build.make:107: src/CMakeFiles/xdg-desktop-portal-lxqt.dir/filedialoghelper.cpp.o] Error 1
make[3]: *** Waiting for unfinished jobs....
In file included from /<<PKGBUILDDIR>>/src/filedialoghelper.h:28,
                 from /<<PKGBUILDDIR>>/src/filechooser.cpp:32:
/usr/include/libfm-qt/filedialoghelper.h:5:10: fatal error: qpa/qplatformdialoghelper.h: No such file or directory
    5 | #include <qpa/qplatformdialoghelper.h> // this private header is subject to changes
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.

$ apt-file find qpa/qplatformdialoghelper.h
qt6-base-private-dev: /usr/include/x86_64-linux-gnu/qt6/QtGui/6.2.4/QtGui/qpa/qplatformdialoghelper.h
qtbase5-private-dev: /usr/include/x86_64-linux-gnu/qt5/QtGui/5.15.4/QtGui/qpa/qplatformdialoghelper.h
qtbase5-private-gles-dev: /usr/include/x86_64-linux-gnu/qt5/QtGui/5.15.4/QtGui/qpa/qplatformdialoghelper.h

Drive-by as I'm currently working on packaging this.