Fix Demo test rebuilds

tests/Demo.cpp

@@ -239,7 +239,12 @@ class DemoWindow : public StandaloneWindow,
     static const int kSidebarWidth = 81;
 
 public:
-    static constexpr const char* const kExampleWidgetName = "Demo";
+#ifdef DGL_CAIRO
+    static constexpr const char* const kExampleWidgetName = "Demo - Cairo";
+#endif
+#ifdef DGL_OPENGL
+    static constexpr const char* const kExampleWidgetName = "Demo - OpenGL";
+#endif
 
     DemoWindow(Application& app)
         : StandaloneWindow(app),

tests/Makefile

@@ -133,5 +133,8 @@ clean:
 # ---------------------------------------------------------------------------------------------------------------------
 
 -include $(OBJS:%.o=%.d)
+-include ../build/tests/Demo.cpp.cairo.d
+-include ../build/tests/Demo.cpp.opengl.d
+-include ../build/tests/Demo.cpp.vulkan.d
 
 # ---------------------------------------------------------------------------------------------------------------------