Use debian-slim based image for pipeline runner

.gitlab-ci.yml

 # CI pipeline configuration
 
 default:
-  image: gmulas/np-tmcode
+  image: debian:bookworm-slim
 
 # Switch from branch pipelines to merge request pipelines when a merge request is created
 workflow:
@@ -34,14 +34,20 @@ building_stage:
          - ".git*"
          - ".git/**/*"
       expire_in: 2 hours
+   tags:
+     - saas-linux-small-amd64
    script:
       # bash commands to be executed
       - pwd
       - hostname
       - echo $CI_COMMIT_SHA
       - echo $CI_COMMIT_BRANCH
+      - echo "Updating system"
+      - apt update
+      - echo "Installing dependencies"
+      - apt install -y g++ gfortran make
       - cd src
-      - echo "Running make (ONLY C++ CODE)"
+      - echo "Running make"
       - make
 
 running_stage:
@@ -58,12 +64,18 @@ running_stage:
          - ".git*"
          - ".git/**/*"
       expire_in: 2 hours
+   tags:
+     - saas-linux-small-amd64
    script:
       # bash commands to be executed
       - pwd
       - hostname
       - echo $CI_COMMIT_SHA
       - echo $CI_COMMIT_BRANCH
+      - 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
@@ -86,12 +98,18 @@ testing_stage:
          - ".git*"
          - ".git/**/*"
       expire_in: 2 hours
+   tags:
+     - saas-linux-small-amd64
    script:
       # bash commands to be executed
       - pwd
       - hostname
       - echo $CI_COMMIT_SHA
       - echo $CI_COMMIT_BRANCH
+      - 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"