run example1 on aarch64 with openglES3 failed

I cross compiled nanogui on aarch64 success, but when I run the example1 , and try to open a file dialog, I get error as
```
Caught exception in event handler: nanogui::file_dialog(): dialog error: The name org.freedesktop.portal.Desktop was not provided by any .service files
```
besides no dialog window open. I use weston default on the embedded device.