gdm: sv check dbus is enough now as there's a check script

srcpkgs/gdm/files/gdm/run

@@ -1,5 +1,4 @@
 #!/bin/sh
-# Test if dbus is running
-dbus-send --system / org.freedesktop.DBus.Peer.Ping >/dev/null 2>&1 || exit 1
+sv check dbus || exit 1
 [ ! -d /run/gdm ] && mkdir -m0711 -p /run/gdm && chown root:gdm /run/gdm
 exec gdm

srcpkgs/gdm/template

@@ -1,7 +1,7 @@
 # Template file for 'gdm'
 pkgname=gdm
 version=3.16.4
-revision=3
+revision=4
 patch_args="-Np1"
 build_style=gnu-configure
 configure_args="$(vopt_enable gir introspection)