gnu: qt@5: Update to 5.15.8.
* gnu/packages/qt.scm (%qt-version): New variable.
(qtbase-5, qt3d-5, qtsvg-5, qtimageformats, qtx11extras, qtxmlpatterns,
qtdeclarative-5, qtconnectivity, qtwebsockets-5, qtsensors, qtmultimedia-5,
qtwayland-5, qtserialport, qtserialbus, qtwebchannel-5, qtwebglplugin,
qtwebview, qtlocation, qttools-5, qtscript, qtquickcontrols-5,
qtgraphicaleffects, qtgamepad, qtscxml, qtpurchasing, qtcharts,
qtdatavis3d, qtnetworkauth-5, qtremoteobjects, qtspeech, qtwebengine,
python-pyqt, python-pyqtwebengine, python-shiboken-2):
Update to 5.15.8 by using the new variable.
2ac51ec99b