core-deps-3.14/3.16/3.18: Remove libxkbcommon autogenargs

The --with-xkb-config-root option is not needed because its configure
script already uses 'pkg-config --variable=xkb_base xkeyboard-config' to
get the value. We should stop using this option to prevent gnome-shell from
crashing on systems which does not have xkeyboard-config installed in
the expected location.

https://bugzilla.gnome.org/show_bug.cgi?id=735988