[OpenMesh] cmake CMakeLists.txt Qt 5.15.1

usr/include/qt5/QtCore/qstring.h:2135:18: error: no declaration matches ‘qsizetype QStringView::count(QChar, Qt::CaseSensitivity) const’ 2135 | inline qsizetype QStringView::count(QChar c, Qt::CaseSensitivity cs) const noexcept | ^~~~~~~~~~~ Mfg th.diebels