This allow Weston to be build without the clients.
(From OE-Core rev: a3084bd681f67b28b4e4b44ba0c6a281800f719d)
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>