{
  "windows" : {
    "chef_version"  : "latest",
    "download_url"  : "https://www.opscode.com/chef/download?p=windows&pv=2008r2&m=x86_64",
    "machine_os"    : "2008r2",
    "machine_arch"  : "x86_64"
  },
  "ubuntu" : {
    "chef_version"  : "latest",
    "download_url"  : "https://opscode-omnibus-packages.s3.amazonaws.com/ubuntu/13.04/x86_64/chef_11.10.4-1.ubuntu.13.04_amd64.deb",
    "machine_os"    : "ubuntu",
    "machine_arch"  : "x86_64"
  },
  "centos" : {
    "chef_version"  : "latest",
    "download_url"  : "https://opscode-omnibus-packages.s3.amazonaws.com/el/6/x86_64/chef-11.4.0-1.el6.x86_64.rpm",
    "machine_os"    : "centos",
    "machine_arch"  : "x86_64"
  }
}
{
  "windows" : {
    "chef_version"  : "latest",
    "download_url"  : "https://www.opscode.com/chef/download?p=windows&pv=2008r2&m=x86_64",
    "machine_os"    : "2008r2",
    "machine_arch"  : "x86_64"
  },
  "ubuntu" : {
    "chef_version"  : "latest",
    "download_url"  : "https://opscode-omnibus-packages.s3.amazonaws.com/ubuntu/13.04/x86_64/chef_11.12.4-1_amd64.deb",
    "machine_os"    : "ubuntu",
    "machine_arch"  : "x86_64"
  },
  "centos" : {
    "chef_version"  : "latest",
    "download_url"  : "https://opscode-omnibus-packages.s3.amazonaws.com/el/6/x86_64/chef-11.12.4-1.el6.x86_64.rpm",
    "machine_os"    : "centos",
    "machine_arch"  : "x86_64"
  }
}

Add latest chef-client download url to build.json
Add latest chef-client download url to build.json