DebugHelper: Disable 'Build All' button if there isn't anything to build

Task-number: QTCREATORBUG-4176

src/plugins/qt4projectmanager/qtoptionspage.cpp

@@ -575,10 +575,14 @@ void QtOptionsPageWidget::updateDebuggingHelperUi()
         const bool hasLog = currentItem && !currentItem->data(0, BuildLogRole).toString().isEmpty();
         m_debuggingHelperUi->showLogButton->setEnabled(hasLog);
 
-        m_debuggingHelperUi->rebuildButton->setEnabled(!isBuildingGdbHelper
-                                                       && !isBuildingQmlDumper
-                                                       && !isBuildingQmlDebuggingLib
-                                                       && !isBuildingQmlObserver);
+        m_debuggingHelperUi->rebuildButton->setEnabled((!isBuildingGdbHelper
+                                                        && !isBuildingQmlDumper
+                                                        && !isBuildingQmlDebuggingLib
+                                                        && !isBuildingQmlObserver)
+                                                       && (canBuildGdbHelper
+                                                           || canBuildQmlDumper
+                                                           || canBuildQmlDebuggingLib
+                                                           || canBuildQmlObserver));
 
         m_ui->debuggingHelperWidget->setVisible(true);
     }