Debugger: Fix visibility of Debugging Helper Dialog

Task-number: QTCREATORBUG-8440
Done-with: David Schulz

Change-Id: Iccd252cc743df37216884cbc0e5a51c96ac382b4
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/debugger/gdb/classicgdbengine.cpp

@@ -1278,6 +1278,9 @@ static void showQtDumperLibraryWarning(const QString &details)
         "expand the Details section and click Build All."));
     if (!details.isEmpty())
         dialog.setDetailedText(details);
+#if defined(Q_OS_MAC) && QT_VERSION >= 0x050000
+    dialog.setWindowModality(Qt::WindowModal);
+#endif
     dialog.exec();
     if (dialog.clickedButton() == qtPref) {
         Core::ICore::showOptionsDialog(