wic: align layer plugin path
wic look for external layer source plugin under scripts/lib/
while other tools look for lib/.
allow wic to check for source plugin at both scripts/lib/ and
lib/ to align with other tools while avoid breaking any existing
source plugin in external layer.
[YOCTO #13056]
Signed-off-by: Lee Chee Yang <chee.yang.lee@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit
986baff26bd96a6265f5fe2d631818fff9f66374)
Signed-off-by: Armin Kuster <akuster808@gmail.com>
