Also test against the 2.9 release

.gitlab-ci.yml

@@ -24,6 +24,18 @@ dune:2.8  clang  C++17:
   variables:
     DUNECI_BRANCH: releases/2.8
 
+dune:2.9 gcc C++20:
+  image: registry.dune-project.org/docker/ci/dune:2.9-debian-11-gcc-10-20
+  script: duneci-standard-test
+  variables:
+    DUNECI_BRANCH: releases/2.9
+
+dune:2.9  clang  C++17:
+  image: registry.dune-project.org/docker/ci/dune:2.9-debian-11-clang-11-20
+  script: duneci-standard-test
+  variables:
+    DUNECI_BRANCH: releases/2.9
+
 dune:git  clang  C++17:
   image: registry.dune-project.org/docker/ci/dune:git-debian-10-clang-7-libcpp-17
   script: duneci-standard-test