include: choose package output directory based on repository info

Use the new repository metadata field to choose the output directory of the
final package archives.

Non-sharable packages will be placed in the per-target package directory
while the rest will be placed in a per-repository sub directory within the
$OUTPUT_DIR/packages/$CPU_TYPE/ prefix.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>