L2SS-259: Try ubuntu:20.04 instead of docker compose image

.gitlab-ci.yml

@@ -13,7 +13,7 @@ stages:
   - unit-tests
 building:
   stage: building
-  image: docker/compose:latest
+  image: ubuntu:20.04
   variables:
     CHECKOUT_DIR: "$CI_PROJECT_DIR/../"
     TANGO_SKA_LOCAL_DIR: "${CHECKOUT_DIR}"
@@ -26,7 +26,7 @@ building:
     NETWORK_MODE: "lofar"
   before_script:
     - sudo apt-get update
-    - sudo apt-get install -y git make
+    - sudo apt-get install -y git make docker-compose
     - touch ~/.Xauthority
   script:
     - cd docker-compose