This reverts commit d1ad9e1ea2.
The empty directory `local_packages` was there for a reason.
`simple-cdd` gives a warning when this directory doesn't exist:
WARNING local package source /home/kali/live-build-config/simple-cdd/local_packages is neither a file nor a directory
So re-instate this empty dir to keep the logs clean.
I assume that `variant-minimal` was also there for a good reason.