nixos.podman: Expose extraPackages from the podman wrapper

nixos/modules/virtualisation/podman.nix

@@ -4,18 +4,20 @@ let
 
   inherit (lib) mkOption types;
 
+  podmanPackage = (pkgs.podman.override { inherit (cfg) extraPackages; });
+
   # Provides a fake "docker" binary mapping to podman
-  dockerCompat = pkgs.runCommandNoCC "${pkgs.podman.pname}-docker-compat-${pkgs.podman.version}" {
+  dockerCompat = pkgs.runCommandNoCC "${podmanPackage.pname}-docker-compat-${podmanPackage.version}" {
     outputs = [ "out" "bin" "man" ];
-    inherit (pkgs.podman) meta;
+    inherit (podmanPackage) meta;
   } ''
     mkdir $out
 
     mkdir -p $bin/bin
-    ln -s ${pkgs.podman.bin}/bin/podman $bin/bin/docker
+    ln -s ${podmanPackage.bin}/bin/podman $bin/bin/docker
 
     mkdir -p $man/share/man/man1
-    for f in ${pkgs.podman.man}/share/man/man1/*; do
+    for f in ${podmanPackage.man}/share/man/man1/*; do
       basename=$(basename $f | sed s/podman/docker/g)
       ln -s $f $man/share/man/man1/$basename
     done
@@ -54,6 +56,19 @@ in
       '';
     };
 
+    extraPackages = mkOption {
+      type = with types; listOf package;
+      default = [ ];
+      example = lib.literalExample ''
+        [
+          pkgs.gvisor
+        ]
+      '';
+      description = ''
+        Extra packages to be installed in the Podman wrapper.
+      '';
+    };
+
     libpod = mkOption {
       default = {};
       description = "Libpod configuration";
@@ -77,12 +92,11 @@ in
 
   config = lib.mkIf cfg.enable {
 
-    environment.systemPackages = [ pkgs.podman ]
+    environment.systemPackages = [ podmanPackage ]
       ++ lib.optional cfg.dockerCompat dockerCompat;
 
     environment.etc."containers/libpod.conf".text = ''
       cni_plugin_dir = ["${pkgs.cni-plugins}/bin/"]
-      cni_config_dir = "/etc/cni/net.d/"
 
     '' + cfg.libpod.extraConfig;