xserver_xorg-server: fix missing backslash on end of CONF_OPT

This patch adds a missing backslash on a line in the middle of the list of
XSERVER_XORG_SERVER_CONF_OPT.

Reported-by: Sebastian Matuschka <Sebastian.Matuschka@gcd-solutions.de>

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

@@ -48,7 +48,7 @@ XSERVER_XORG_SERVER_CONF_OPT = $(XSERVER_XORG_ENABLE_KDRIVE) \
 		--enable-freetype $(XSERVER_XORG_ENABLE_MODULAR) \
 		--disable-config-hal $(XSERVER_XORG_MESA_DIR) \
 		--disable-xnest --disable-xephyr --disable-xvfb \
-		$(XSERVER_XORG_NULL_CURSOR)
+		$(XSERVER_XORG_NULL_CURSOR) \
 		CFLAGS="-I$(STAGING_DIR)/usr/include/pixman-1"
 
 XSERVER_XORG_SERVER_INSTALL_STAGING_OPT = DESTDIR=$(STAGING_DIR) install install-data