DOCKER_BUILDKIT=0 is depracated

[EveningStarlight]

The classic build option DOCKER_BUILDKIT=0 is deprecated and will eventually lose support.

Moving to the new version, by removing this flag, was briefly tested.
Two images have issues with the new build, remote-desktop and sas,
who both have Out of Memory errors when trying to export the layers.

Possible options for solving the error:

• Set the parallelism to 1: no improvement
• Set memory limits: no improvement
• Disable caching: no improvement
• use --output=type=docker: no improvement
• Increase the runner size
• Minimize the number of layers created by the Dockerfile