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/dialogs/filesyncdialog.cpp

@@ -104,7 +104,7 @@ static QWidget * folderSelectorWidget(QLineEdit * le, QWidget * parent)
   l->addWidget(btn);
 
   QObject::connect(btn, &QToolButton::clicked, [=]() {
-    QString dir = QFileDialog::getExistingDirectory(parent, fsw->property("fileDialogTitle").toString(), le->text(), 0);
+    QString dir = QFileDialog::getExistingDirectory(parent, fsw->property("fileDialogTitle").toString(), le->text());
     if (!dir.isEmpty()) {
       le->setText(QDir::toNativeSeparators(dir));
       le->setFocus();