GitLab

When we switched to a newer kernel version in c64d3d0e, the
cleanup_images.sh script no longer removed the linux kernel source
folder, since it still used the old version number. Now, I use a regex
to avoid this issue in the future.

This will push the images built by docker-images and docker-images-debug
target, if they exist.

This will result in make docker-images directly generating images with
appropriate tags.

simbricks/simbricks additionally with gem5.opt installed in addition to
gem5.fast. About 1.1GB larger.

(this image takes very long to build)

increases connection limits, disables host fingerprint checking, enables persistent connections

Removes source and objects for qemu and linux kernel, packer cache, and
raw images.