package/xserver_xorg-server: add condition in xserver_xorg-server.mk

Does not install systemd unit if nodm or xdm is enabled.

Signed-off-by: Yanghao Cheng <yanghao.cheng@aioi-atg.com>
[yann.morin.1998@free.fr:
  - don't use $(or ...)
  - slightly reword comment
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit 6898ca03a25c4577c1848d6217c7d7a99354c031)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/x11r7/xserver_xorg-server/xserver_xorg-server.mk

@@ -176,10 +176,14 @@ XSERVER_XORG_SERVER_CONF_OPTS += --with-sha1=libsha1
 XSERVER_XORG_SERVER_DEPENDENCIES += libsha1
 endif
 
+# Install the systemd unit only when nodm nor xdm aren't enabled, as
+# they would be responsible for starting the server.
+ifeq ($(BR2_PACKAGE_NODM)$(BR2_PACKAGE_XAPP_XDM),)
 define XSERVER_XORG_SERVER_INSTALL_INIT_SYSTEMD
 	$(INSTALL) -D -m 0644 package/x11r7/xserver_xorg-server/xorg.service \
 		$(TARGET_DIR)/usr/lib/systemd/system/xorg.service
 endef
+endif
 
 # Install the init script only when neither nodm nor xdm are enabled, as
 # they would be responsible for starting the server.