compiling Core in the CI with cmake

.gitlab-ci.yml

@@ -22,4 +22,7 @@ cmake:
         - source /cvmfs/cms.cern.ch/cmsset_default.sh
         - yum install -y cmake3 python3 zsh
         - ./install.sh
-
+        - cd CMSSW*/
+        - shopt -s expand_aliases  # allows aliases like cmsenv to be used
+        - cmsenv
+        - scram b -j$(nproc)