Try another workaround: install qmake and replace g++ conf files by clang's
the export QMAKESPEC=/usr/lib/x86_64-linux-gnu/qt5/mkspecs/linux-clang/ wasn't enough it seems (but it worked for me locally :/)
the export QMAKESPEC=/usr/lib/x86_64-linux-gnu/qt5/mkspecs/linux-clang/ wasn't enough it seems (but it worked for me locally :/)