use clang-18 image for build-examples

.gitlab-ci.yml

@@ -5,11 +5,14 @@ stages:
 
 
 build-examples:
-  image: i10git.cs.fau.de:5005/pycodegen/pycodegen/nox:alpine
+  image: i10git.cs.fau.de:5005/walberla/buildenvs/clang-18:latest
   tags:
     - docker
   stage: "Test"
   needs: []
+  variables:
+    CXX": clang++
+    CC: clang
   script:
     - cd user_manual/examples
     - cmake -S . -B build