Command not found error when installing Dockerfile

Hi,

I made a local clone of this docker repository and followed the instructions in README. However, I encountered the following error:

```

randychen@RANDY-DESKTOP:~/robust_vo/DPVO_Docker$ sudo ./build_container.sh 12.6.1
sudo: ./build_container.sh: command not found
```

I wonder how I should get around this? Thanks!