fix building under linux

src/overlaycontroller.cpp

@@ -28,6 +28,8 @@ namespace advsettings {
 
 std::unique_ptr<OverlayController> OverlayController::singleton;
 
+constexpr const char* OverlayController::applicationVersionString;
+
 QSettings* OverlayController::_appSettings = nullptr;
 
 OverlayController::~OverlayController() {

src/tabcontrollers/ChaperoneTabController.cpp

@@ -1,6 +1,7 @@
 #include "ChaperoneTabController.h"
 #include <QQuickWindow>
 #include "../overlaycontroller.h"
+#include <math.h>
 
 // application namespace
 namespace advsettings {

src/utils/ChaperoneUtils.cpp

@@ -1,6 +1,7 @@
 
 #include "ChaperoneUtils.h"
 #include <iostream>
+#include <math.h>
 
 namespace utils {