[v20.05] Backport CI changes
At least "CI: return output of common.run_pmbootstrap" is needed to fix botched backport for the aport-lint job on v20.05: https://gitlab.com/postmarketOS/pmaports/-/jobs/721432978
At least "CI: return output of common.run_pmbootstrap" is needed to fix botched backport for the aport-lint job on v20.05: https://gitlab.com/postmarketOS/pmaports/-/jobs/721432978