snap: core20 and nested_virtualization CI

.cirrus.yml

@@ -1,16 +1,15 @@
 task:
   use_compute_credits: true
-  container:
-    image: ubuntu:18.04
-    cpu: 1
+  compute_engine_instance:  # https://cirrus-ci.org/guide/custom-vms/#custom-compute-engine-vms
+    image_project: ubuntu-os-cloud
+    image: family/ubuntu-2404-lts-amd64  # https://cloud.google.com/compute/docs/images/os-details#ubuntu_lts
+    nested_virtualization: true
+    cpu: 4  # 1 is enough, but nested_virtualization machines have at least 4
     memory: 2G
   timeout_in: 20m
-  env:
-    DOCKER_PACKAGES: "snapcraft"
-  install_packages_script:
-    - apt-get update
-    - apt-get install --no-install-recommends --no-upgrade -qq $DOCKER_PACKAGES
   snapcraft_pull_script:
+    - snap install snapcraft --classic
+    - snap install multipass
     - snapcraft pull
   ci_script:
     - snapcraft

snap/snapcraft.yaml

@@ -8,7 +8,7 @@ description: |
 
 grade: stable
 confinement: strict
-base: core18
+base: core20
 
 apps:
   daemon: