Use PACKAGECONFIG to offer some flexibility to the libmatchbox configuration,
and remove two spurious build dependencies (expat and libstartup-notification).
(From OE-Core rev: 8505f0fa48cc79d51616b923c6e2c778c4b46a44)
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>