Set proc number to 4 while testing khiops installation

.github/actions/test-khiops-install/action.yml

@@ -8,10 +8,19 @@ runs:
   steps:
     - name: Print status for debugging
       shell: bash
-      run: khiops-env --env
+      # We force the process number to 4 because the runner has only 2 proc.
+      # With 2 proc khiops-env switch to serial and mpi is not used.
+      # The env var OMPI_MCA_rmaps_base_oversubscribe is for openmpi it corresponds to
+      # the flag --oversubscribe (Nodes are allowed to be oversubscribed)
+      run: |
+        export OMPI_MCA_rmaps_base_oversubscribe=true
+        export KHIOPS_PROC_NUMBER=4
+        khiops-env --env
     - name: Check Khiops output
       shell: bash
       run: |
+        export OMPI_MCA_rmaps_base_oversubscribe=true
+        export KHIOPS_PROC_NUMBER=4
         khiops -s
         khiops -v &> output
         LINE_NUMBER=$(wc -l < output)