Revert pipeline to debian-slim distro

.gitlab-ci.yml

 # CI pipeline configuration
 
-default:
-  image: debian:bookworm-slim
-
 # Switch from branch pipelines to merge request pipelines when a merge request is created
 workflow:
   rules:
@@ -25,6 +22,7 @@ stages:
 building_stage:
    stage: build
    allow_failure: false
+   image: debian:bookworm-slim
    artifacts:
       paths:
          - build/cluster/*
@@ -42,8 +40,10 @@ building_stage:
       - echo $CI_COMMIT_BRANCH
       - echo "Getting system info ..."
       - cat /etc/os-release
+      - echo "Updating system ..."
+      - apt update
       - echo "Installing dependencies"
-      - sudo yum install -y g++ gfortran make
+      - apt install -y g++ gfortran make
       - cd src
       - echo "Running make"
       - make
@@ -53,6 +53,9 @@ running_stage:
    allow_failure: false
    needs:
       - job: building_stage
+   image: debian:bookworm-slim
+   dependencies:
+      - building_stage
    artifacts:
       paths:
          - build/cluster/*
@@ -68,8 +71,10 @@ running_stage:
       - hostname
       - echo $CI_COMMIT_SHA
       - echo $CI_COMMIT_BRANCH
-      - echo "Updating system"
-      - sudo yum install -y g++ gfortran gdb
+      - echo "Updating system ..."
+      - apt update
+      - echo "Installing dependencies ..."
+      - apt install -y g++ gfortran gdb
       - cd build/sphere
       - echo "Running np_sphere"
       - chmod +x np_sphere
@@ -84,6 +89,9 @@ testing_stage:
    allow_failure: true
    needs:
       - job: running_stage
+   dependencies:
+      - building_stage
+      - running_stage
    artifacts:
       paths:
          - build/cluster/pycompare.html
@@ -98,8 +106,10 @@ testing_stage:
       - hostname
       - echo $CI_COMMIT_SHA
       - echo $CI_COMMIT_BRANCH
-      - echo "Updating system"
-      - sudo yum install -y python3
+      - echo "Updating system ..."
+      - apt update
+      - echo "Installing dependencies ..."
+      - apt install -y python3
       - cd build/sphere
       - export FFILE=../../test_data/sphere/OSPH
       - echo "Comparing output of SPHERE"