xfce4-power-manager: Don't use /run/current-system/sw/bin in org.freedesktop.policykit.exec.path (#485180)

pkgs/by-name/xf/xfce4-power-manager/package.nix

@@ -56,12 +56,15 @@ stdenv.mkDerivation (finalAttrs: {
   # using /run/current-system/sw/bin instead of nix store path prevents polkit permission errors on
   # rebuild.  See https://github.com/NixOS/nixpkgs/issues/77485
   postPatch = ''
-    substituteInPlace src/org.xfce.power.policy.in.in --replace-fail "@sbindir@" "/run/current-system/sw/bin"
     substituteInPlace common/xfpm-brightness-polkit.c --replace-fail "SBINDIR" "\"/run/current-system/sw/bin\""
     substituteInPlace src/xfpm-suspend.c --replace-fail "SBINDIR" "\"/run/current-system/sw/bin\""
   '';
 
-  configureFlags = [ "--enable-maintainer-mode" ];
+  configureFlags = [
+    "--enable-maintainer-mode"
+    "--sbindir=\${out}/bin"
+  ];
+
   enableParallelBuilding = true;
 
   passthru.updateScript = gitUpdater {