package/libxkbcommon: fix builds with/without X11

We need to explicitly disable X11 support when X11 is not available.
Conversely, when it is, we need to add the required dependencies.

Fixes a slew of autobuild failures:
    http://autobuild.buildroot.org/results/587/58794f894a4950b77e38d5fc877852d6cc507d8c/
    http://autobuild.buildroot.org/results/927/92741f6b9b7909b226c200e453ac6cee8af5abd6/
    http://autobuild.buildroot.org/results/51c/51cb09f7f267319948c685f905e29afe99f59589/
    ...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Fatih Aşıcı <fatih.asici@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libxkbcommon/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_LIBXKBCOMMON
 	bool "libxkbcommon"
+	select BR2_PACKAGE_LIBXCB if BR2_PACKAGE_XORG7
 	help
 	  xkbcommon is a keymap compiler and support library which
 	  processes a reduced subset of keymaps as defined by the XKB

package/libxkbcommon/libxkbcommon.mk

@@ -15,4 +15,11 @@ LIBXKBCOMMON_DEPENDENCIES = host-bison host-flex
 # uses C99 features
 LIBXKBCOMMON_CONF_ENV = CFLAGS="$(TARGET_CFLAGS) -std=gnu99"
 
+ifeq ($(BR2_PACKAGE_XORG7),y)
+LIBXKBCOMMON_CONF_OPTS += --enable-x11
+LIBXKBCOMMON_DEPENDENCIES += libxcb
+else
+LIBXKBCOMMON_CONF_OPTS += --disable-x11
+endif
+
 $(eval $(autotools-package))