fix(build_library): use https://public.update.core-os.net now

We added a new https certificate on the new update service and changed
the hostname to be consistent with all of the other endpoints. Update
the new images to use this.

The old URL http://public.roller.core-os.net will remain working until
all of the old client have been updated.
Merge pull request #220 from skarllot/master

Small fix to contrib VirtualBox script
fix(setup_board): Allow make.conf.user to be per-board

Previously this would symlink to a global make.conf.user making it
impossible to apply changes to a board but not the SDK.
Merge pull request #223 from marineam/user

fix(setup_board): Allow make.conf.user to be per-board
fix(build_image): Only use 'alpha' group in official builds.
Merge pull request #222 from marineam/group

fix(build_image): Only use 'alpha' group in official builds.
fix(set_lsb_release): Set bug report url.
Merge pull request #225 from marineam/bugs

fix(set_lsb_release): Set bug report url.
feat(vm_image_util): Adding support for openstack and brightbox

Added USE flags for specifying the provider (ec2, openstack, or brightbox).
Merge pull request #224 from crawford/oems

feat(vm_image_util): Adding support for openstack and brightbox
fix(qemu_template): Replace getopts with simple pattern matching.

The use of getopts was leading to conflicts between this script's short
options and qemu's long options. For example -serial was getting
interpreted as -s -- erial which is not very helpful.
feat(qemu_template): Provide SSH keys via config drive

Moving away from our old behavior of loading 'authorized_keys' on virtfs
volumes. Still using virtfs to avoid depending on mkisofs or similar.
feat(qemu_template): Add support for user-provided configs.

A custom cloud config can be provided directly via -u or as an existing
config drive image via -c.
fix(release_util): Compress vhd images.
fix(make_chroot): Add new repos.conf and crossdev metadata

The latest release of portage uses repos.conf, so generate that
file when making the chroot. The crossdev overlay also needed
repo_name and layout.conf files.
Merge pull request #219 from crawford/new_portage

fix(make_chroot): Add new repos.conf and crossdev metadata
Merge pull request #226 from marineam/vhd

fix(release_util): Compress vhd images.
Merge pull request #214 from marineam/units

Config drive for QEMU
fix(vm_image_util): Fix DIGESTS path for compressed vhd images.

Missed this in eb72b6e5
Merge pull request #227 from marineam/vhd

fix(vm_image_util): Fix DIGESTS path for compressed vhd images.