Default amd64 builds to use amd64 runner tag instead of untagged runners

The community dynamic and static runners are currently configured to run untagged jobs. There is no way for a package to specify that a build should be done on a runner with a tag such as "amd64-extra-privileged".

This change will force builds to use the dynamic runners. There are now different runners with various instance sizes and disk sizes to speed up builds and also keep costs under control.