build: add os package installation before script.

.gitlab-ci.yml

@@ -72,6 +72,8 @@ before_script:
     echo -e "\033[35;1m Using branch $CHILD_PIPELINE_BRANCH of BEC Widgets \033[0;m";
     test -d bec_widgets || git clone --branch $CHILD_PIPELINE_BRANCH https://gitlab.psi.ch/bec/bec_widgets.git; cd bec_widgets;
     fi
+  - *install-os-packages
+  - *install-qt-webengine-deps
 
 formatter:
   stage: Formatter