Reject SSH connections without SLURM allocation

Reviewed-by: Aleix Boné <abonerib@bsc.es>

pkgs/overlay.nix

@@ -39,6 +39,18 @@ final: prev:
       # See https://bugs.schedmd.com/show_bug.cgi?id=19324
       ./slurm-rank-expansion.patch
     ];
+    # Install also the pam_slurm_adopt library to restrict users from accessing
+    # nodes with no job allocated.
+    postBuild = (old.postBuild or "") + ''
+      pushd contribs/pam_slurm_adopt
+        make "PAM_DIR=$out/lib/security"
+      popd
+    '';
+    postInstall = (old.postInstall or "") + ''
+      pushd contribs/pam_slurm_adopt
+        make "PAM_DIR=$out/lib/security" install
+      popd
+    '';
   });
 
   prometheus-slurm-exporter = prev.callPackage ./slurm-exporter.nix { };