Compile the dnet tool for Linux (x86, amd64 and arm)
and Windows (x86 and amd64)
- Moved installation of dependencies into `Dockerfile.build`
- Remove `start-services` from Makefile
- That's the responsibility of Docker or build environment
- Removed utils depending on `netlink` from `netutils/utils.go`
Unable to add `make cross` to CircleCI just yet as there are some
issues to solve that are unrelated to this PR
Also fix `.gitignore` which was not updated after changing the build
image name in #667
Signed-off-by: Dave Tucker <dt@docker.com>
