build: handle stable branch
build: handle stable branch

If we build from the stable branch we want to fetch the artifact for the
coresponding build on the master branch. The stable branch doesn't produce artifacts
with a branch prefix because it is just a subset of the commits on master
that have passed the tests.

mbeddr/mbeddr.core,mbeddr/mbeddr.core,mbeddr/mbeddr.core,mbeddr/mbeddr.core,mbeddr/mbeddr.core