Answer by Günter Zöchbauer for How to include files outside of Docker's build context?

On Linux you can mount other directories instead of symlinking them

mount --bind olddir newdir

See https://superuser.com/questions/842642 for more details.

I don't know if something similar is available for other OSes.I also tried using Samba to share a folder and remount it into the Docker context which worked as well.