Turns out you can specify this using the PACKAGE_CLASSES
variable but you better not list it first.
(From yocto-docs rev: 7fdf5f9fcf026503cdedd906cd7b8c814affa81d)
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>