Qt5 build does not work on Gentoo

[HJarausch]

Hi,
I'm unable to build SmartDeblur on my Gentoo system which has only Qt5 (no Qt4 anymore).
I get
CMake Error at /usr/share/cmake/Modules/FindQt4.cmake:1323 (message):
Found unsuitable Qt version "5.12.0" from /usr/bin/qmake, this code
requires Qt 4.x

Many thanks for a hint,
Helmut

[Sciss]

The following works on Debian where Qt5 is installed:

mkdir build
cd build
/usr/lib/x86_64-linux-gnu/qt5/bin/qmake ../src/SmartDeblur.pro
make -j2
./SmartDeblur