rosenthal: Add libseat-sans-logind.

* rosenthal/packages/admin.scm: New file.
(libseat-sans-logind): New variable.

rosenthal/packages/admin.scm

@@ -0,0 +1,21 @@
+;; SPDX-FileCopyrightText: 2022 Hilton Chain <hako@ultrarare.space>
+;;
+;; SPDX-License-Identifier: GPL-3.0-or-later
+
+(define-module (rosenthal packages admin)
+  #:use-module (guix gexp)
+  #:use-module (guix packages)
+  #:use-module (guix utils)
+  #:use-module (gnu packages admin))
+
+(define-public libseat-sans-logind
+  (let ((base libseat))
+    (package
+      (inherit base)
+      (name "libseat-sans-logind")
+      (arguments
+       (substitute-keyword-arguments (package-arguments base)
+         ((#:configure-flags configure-flags)
+          #~(append #$configure-flags
+                    (list "-Dlibseat-logind=disabled")))))
+      (propagated-inputs '()))))