sysroot: Upload to the same folder as the other artifacts

Storing the sysroot artifacts with the others will make it easier to prevent inconsistencies due to image rotations and other factors.

The metadata file pointing to the latest version is kept in the current location as expected by ade, and contains the updated URL pointing to the actual tarball.

• Test job: https://jenkins.apertis.org/job/playground/job/em/job/debos-image-build/18/
• Artifacts: https://images.apertis.org/test/playground/em/debos-image-build/