layer.conf: add a top-level ARAGOBASE variable
layer.conf: add a top-level ARAGOBASE variable

Signed-off-by: Denys Dmytriyenko <d29de71aea38aad3a87d486929cb0aad173ae612@ti.com>

MentorEmbedded/meta-arago,rcn-ee/meta-arago,MentorEmbedded/meta-arago,MentorEmbedded/meta-arago,rcn-ee/meta-arago,rcn-ee/meta-arago,rcn-ee/meta-arago,rcn-ee/meta-arago,MentorEmbedded/meta-arago