fix(gx): remove stub NewGLSDL when compiling for macOS

src/gx/CGxDevice.cpp

@@ -132,10 +132,6 @@ CGxDevice* CGxDevice::NewGLSDL() {
     auto m = SMemAlloc(sizeof(CGxDeviceGLSDL), __FILE__, __LINE__, 0x0);
     return new (m) CGxDeviceGLSDL();
 }
-#else
-CGxDevice* CGxDevice::NewGLSDL() {
-    return nullptr;
-}
 #endif
 
 uint32_t CGxDevice::PrimCalcCount(EGxPrim primType, uint32_t count) {