add new Google Cloud image for the current release

update the create-gce.sh script with the ability to create public images
out of a GS object.

nixos/maintainers/scripts/gce/create-gce.sh

@@ -17,7 +17,19 @@ nix-build '<nixpkgs/nixos/lib/eval-config.nix>' \
 img_path=$(echo gce/*.tar.gz)
 img_name=${IMAGE_NAME:-$(basename "$img_path")}
 img_id=$(echo "$img_name" | sed 's|.raw.tar.gz$||;s|\.|-|g;s|_|-|g')
+img_family=$(echo "$img_id" | cut -d - -f1-4)
+
 if ! gsutil ls "gs://${BUCKET_NAME}/$img_name"; then
   gsutil cp "$img_path" "gs://${BUCKET_NAME}/$img_name"
   gsutil acl ch -u AllUsers:R "gs://${BUCKET_NAME}/$img_name"
+
+  gcloud compute images create \
+    "$img_id" \
+    --source-uri "gs://${BUCKET_NAME}/$img_name" \
+    --family="$img_family"
+
+  gcloud compute images add-iam-policy-binding \
+    "$img_id" \
+    --member='allAuthenticatedUsers' \
+    --role='roles/compute.imageUser'
 fi