chore(cpn): update to Qt 5.15.2 and rework application packaging (#4270)

Co-authored-by: raphaelcoeffic <raphael.coeffic@frafos.com>
Co-authored-by: philmoz <phil.a.mitchell@gmail.com>

companion/src/modeledit/mixerslistwidget.cpp

@@ -275,7 +275,7 @@ void MixerItemViewProxyStyle::drawPrimitive(QStyle::PrimitiveElement element, co
 {
   painter->save();
   if (element == QStyle::PE_IndicatorItemViewItemDrop) {
-    painter->setRenderHint(QPainter::HighQualityAntialiasing, true);
+    painter->setRenderHint(QPainter::Antialiasing, true);
     // set a wider stroke for the drop indicator
     QPen pen(painter->pen());
     pen.setWidthF(2.25f);