add gdbserver to test CI

.github/workflows/tests.yml

@@ -14,9 +14,9 @@ jobs:
     - uses: actions/setup-python@v5
       with:
         python-version: '3.11'
-    - name: Install openmpi and gfortran
+    - name: Install gdbserver and openmpi
       run: |
-        sudo apt install -y libopenmpi-dev
+        sudo apt install -y libopenmpi-dev gdbserver
     - name: Build example mpi program
       run: |
         make -C examples/