test(packer): configure shared directory directly in the image.

This way, we do not always need to use vagrant to start a vm.

tests/packer/init/archlinux-gnome.user-data.yml

@@ -85,3 +85,9 @@ write_files:
     append: true
     content: |
       [[ -f ~/.bash_aliases ]] && source ~/.bash_aliases
+
+  # Setup shared directory
+  - path: /etc/fstab
+    append: true
+    content: |
+      0a31bc478ef8e2461a4b1cc10a24cc4 /home/user/Projects/apparmor.d  virtiofs defaults  0  1