ci: test compilation of slurm plugin

Problem: The slurm plugin is not even compiled in Github CI.

Install libslurm-dev to the list of packages to install in the
ci container and add --with-slurm to the list of configure options.

.github/workflows/main.yml

@@ -22,14 +22,14 @@ jobs:
         ref: ${{ github.event.pull_request.head.sha }}
         fetch-depth: 0
     - name: install dependencies
-      run: sudo apt install libgenders0-dev
+      run: sudo apt install libgenders0-dev libslurm-dev
     - name: fix permissions
       run: chmod -R o-w /home/runner || true
     - name: configure
       run: >
         ./bootstrap &&
         ./configure --with-ssh --with-exec --with-netgroup
-        --with-dshgroups --with-genders --with-machines
+        --with-dshgroups --with-genders --with-machines --with-slurm
     - name: make
       run: make -j 2 CFLAGS="-Werror"
     - name: make check