store Spack's full build logs

try to store all /tmp/spack/spack-stage/*/spack-build-out.txt (would be zero files if everything built correctly I guess) into Gitlab artifacts.

one way could be to store the build logs in the Object Storage with an ID so they can be retrieved at all times

A first implementation has been done with this commit in the build environment repository where the logs of the latest build are kept. In future work we will need to keep the logs of each build run in a separate folder.

mentioned in merge request !105 (merged)

mentioned in commit 2d7de3b3

mentioned in commit 1a1461a0

assigned to @elmath

mentioned in commit fd160d70