xlib_libX11: don't build docs for host

It depends on utils provided by host system, and
they sometimes are missing.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/x11r7/xlib_libX11/xlib_libX11.mk

@@ -18,6 +18,9 @@ XLIB_LIBX11_CONF_OPT = \
 	--with-keysymdef=$(STAGING_DIR)/usr/include/X11/keysymdef.h \
 	--disable-specs
 
+HOST_XLIB_LIBX11_CONF_OPT = \
+	--disable-specs
+
 HOST_XLIB_LIBX11_DEPENDENCIES = host-xproto_xextproto host-libxcb host-xutil_util-macros host-xlib_xtrans host-xlib_libXau host-xlib_libXdmcp host-xproto_kbproto host-xproto_xproto host-xproto_xextproto host-xproto_inputproto host-xproto_xf86bigfontproto xproto_bigreqsproto host-xproto_xcmiscproto
 
 # src/util/makekeys is executed at build time to generate ks_tables.h, so