Remove the dependency on cross from checksum.  This means that checksum
can be called without all binaries being built, but no checksums will
be generate for those binaries.

Output docs to out/docs instead of ./docs since we have real
documentation in that folder now.

This rebases minikube-iso to the release 2017-02.

A change in buildroot required the introduction of a `external.desc` as
multiple external trees are supported in modern buildroot versions. This
required change is described here [0].

[0] https://buildroot.org/downloads/manual/manual.html#br2-external-converting

The existing isolinux.cfg was not included in the config and thus
ignored, include it.

The 4.9.13 kernel included in buildroot 2017-02 is not compatible with
VBox guest additions 5.1.6, thus bump guest additions to 5.1.18.

The defconfig of 4.9.13 has been cleaned up.

systemd 232 included in buildroot 2017-02 is incompatible with docker <
17.03 without boot parameter systemd.legacy_systemd_cgroup_controller=yes
Signed-off-by: NThomas Graf <tgraf@suug.ch>

Fixes https://github.com/kubernetes/minikube/issues/1422

godbus requires the static_build tag when building.  Normal static
compliation doesn't add this go build tag automatically.

	$ make buildroot-image
	$ make out/minikube.iso

- Add en entry in the Makefile for building the container: buildroot-image
- Modify the minikube-iso target to out/minikube.iso to comply with the way
makefiles work.
- Also force the use of a docker container. If not needed
just run IN_DOCKER=1 make out/minikube.iso to avoid the invokation of a docker
container.
- Add some doc.
- The tag added to the generated image will allow to bypass the build of the
image as soon as the container is pushed to the minikube registry.

This makefile dependency is currently only on the folder, not the files
within.  With this PR, the makefile will rebuild the assets when
changes are made to deploy/addons

We are no longer releasing any boot2docker based minikube ISOs.

When changes are made to the ISO folder, rebuild and upload the newly
modified image.  Use this uploaded image as the default in the e2e test
binaries, so that the e2e test suite runs against the PR's changes.

TODO: Subsequent PRs (no changes to ISO) will still run against the
default version in the makefile.  We should figure out if we want to
always run tests against the "latest" image.

This adds a new libmachine API implementation that skips RPC and instead
uses a vendored in driver directly.  This removes the need to download a
separate driver binary.  Currently, only the "core" drivers, and kvm are
supported as vendored in.  This means that xhyve is the only driver that
requires a separate binary for now.

This also tracks the ISO version in the makefile and passes it with
ldflags to automatically bump the default version in the minikube
binary.

This allows us to use vendored dependencies inside the minikube/cmd/main.go file.

Update releases to reflect v1.5.0-beta.1

Before this change, the binary was named `minikube-linux-amd64`,
which is the platform specific artifact name.

When installed through the .deb package, a user expects to have
the `minikube` directly on the `$PATH`.

This change populates the binary as `minikube` in the resulting .deb file.

The makefile was slightly broken for minikube-iso.  Since it && all the
commands to check if buildroot, the git clone failed if the buildroot
folder already existed and broke the target.  I put this logic in a
conditional.