package/wmctrl: x-includes and x-libraries must be set for cross-compiling

set x-includes and x-libraries configure option for cross-compiling.
wmctrl can use poisoned paths if these options are not passed to
configure script.

Fixes:
http://autobuild.buildroot.net/results/7e5/7e5cba8a5650a00e10d1a5528f38cb2bf772aee1

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Jérôme Pouiller <jezz@sysmic.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 046c5e2563)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/wmctrl/wmctrl.mk

@@ -11,4 +11,8 @@ WMCTRL_LICENSE_FILES = COPYING
 
 WMCTRL_DEPENDENCIES = libglib2 xlib_libX11 xlib_libXmu
 
+WMCTRL_CONF_OPTS = \
+	--x-includes=$(STAGING_DIR)/usr/include \
+	--x-libraries=$(STAGING_DIR)/usr/lib
+
 $(eval $(autotools-package))