CMakeLists: Make -Wreorder a compile-time error

This can result in silent logic bugs within code, and given the amount
of times these kind of warnings are caused, they should be flagged at
compile-time so no new code is submitted with them.

src/video_core/renderer_opengl/renderer_opengl.cpp

@@ -315,8 +315,8 @@ public:
 
 RendererOpenGL::RendererOpenGL(Core::Frontend::EmuWindow& emu_window, Core::System& system,
                                Core::Frontend::GraphicsContext& context)
-    : VideoCore::RendererBase{emu_window}, emu_window{emu_window}, system{system},
-      frame_mailbox{}, context{context}, has_debug_tool{HasDebugTool()} {}
+    : RendererBase{emu_window}, emu_window{emu_window}, system{system}, context{context},
+      has_debug_tool{HasDebugTool()} {}
 
 RendererOpenGL::~RendererOpenGL() = default;