make.bash creates a Google Compute Engine VM image to run the Go
FreeBSD builder, booting up to run the buildlet.

make.bash should be run on a Linux box with qemu and a few additional packages.
on ubuntu 16.04 / debian 9 install:
  apt-get install qemu-system-x86 qemu-utils sgabios expect genisoimage

After it completes, it creates a file freebsd-amd64-gce101.tar.gz

Then:
    gsutil cp -a public-read freebsd-amd64-103.tar.gz gs://go-builder-data/freebsd-amd64-103.tar.gz
Or just use the web UI at:
    https://console.developers.google.com/project/symbolic-datum-552/storage/browser/go-builder-data/

Then:
   gcloud compute --project symbolic-datum-552 images delete freebsd-amd64-103
   gcloud compute --project symbolic-datum-552 images create freebsd-amd64-103 --source-uri gs://go-builder-data/freebsd-amd64-103.tar.gz

The VM needs to be run with the GCE metadata attribute "buildlet-binary-url" set to a URL
of the FreeBSD buildlet (cross-compiled, typically).

    buildlet-binary-url == http://storage.googleapis.com/go-builder-data/buildlet.freebsd-amd64
