Add IBM Cloud disk artifacts to stream metadata

[dustymabe]

No description provided.

[dustymabe]

hold for now until I confirm coreos/fedora-coreos-releng-automation#124 is working correctly.

[jlebon]

Looks sane to me.

[dustymabe]

Ran this against the latest next-devel (which contains ibmcloud artifacts) and it looks good. This was the command I ran:

$ ./fedora-coreos-stream-generator -releases=https://fcos-builds.s3.amazonaws.com/prod/streams/next-devel/releases.json -pretty-print | jq .architectures.x86_64.artifacts.ibmcloud
{
  "release": "32.20200927.10.0",
  "formats": {
    "qcow2.xz": {
      "disk": {
        "location": "https://builds.coreos.fedoraproject.org/prod/streams/next-devel/builds/32.20200927.10.0/x86_64/fedora-coreos-32.20200927.10.0-ibmcloud.x86_64.qcow2.xz",
        "signature": "https://builds.coreos.fedoraproject.org/prod/streams/next-devel/builds/32.20200927.10.0/x86_64/fedora-coreos-32.20200927.10.0-ibmcloud.x86_64.qcow2.xz.sig",
        "sha256": "1aacc477c9c81f2aa6c176093d542472969df15ba8d5c6eaa6d1fc64963a3d43"
      }
    }
  }
}