feat: add gdb to sysadmin tooling

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>

common/sysadmin/default.nix

@@ -20,6 +20,8 @@ in
         bcc
         tcpdump
         ncdu
+        # Useful to invoke `coredumpctl gdb`
+        gdb
       ] ++ lib.optional (lib.hasAttr "pwru" pkgs) pkgs.pwru;
     };
   }