meta-alchemy: conf: PACKECONFIG as default values
meta-alchemy: conf: PACKECONFIG as default values

Don't use a variable assignment (=) but a default value (?=) for the
default PACKAGECONFIG values so that it can be overridden in the
local.conf file.

Signed-off-by: Joerg Hofrichter <64f05fd09614173ff715799ea05b4b0d8fbec0da@ni.com>

EttusResearch/meta-ettus,EttusResearch/meta-ettus,EttusResearch/meta-ettus,EttusResearch/meta-ettus,EttusResearch/meta-ettus,EttusResearch/meta-ettus