- upgrades dotnet6-stage0 to 6.0.120
- re-enable s390x
dotnet6 on 3.17 supported s390x. s390x was initially disabled during release of 3.18 due to space-issues on builder. Now that the release is over, it is safe to re-enable. I also wonder if the space issues were eventually resolved so that 3.19 release wont have the same issues.