ci(azure-pipelines): add BuildKit test job

azure-pipelines.yaml

@@ -16,7 +16,7 @@ jobs:
       echo Add other tasks to build, test, and deploy your project.
       echo See https://aka.ms/yaml
     displayName: 'Run a multi-line script'
-- job: ContainerTest
+- job: DockerTaskTest
   container:
     image: 'devfra.azurecr.io/de.fraport.trusted/ubuntu:22.04'
     endpoint: devfra
@@ -28,3 +28,13 @@ jobs:
         Dockerfile: docker/backend/Dockerfile
         buildContext: .
         tags: backend
+- job: BuildKitTest
+  container:
+    image: 'devfra.azurecr.io/de.fraport.trusted/buildkit:0.12.1'
+    endpoint: devfra
+  steps:
+    - script: buildctl build \
+        --frontend=dockerfile.v0 \
+        --local context=. \
+        --local dockerfile=docker/backend/Dockerfile
+      displayName: BuildKit test