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:

• [x] Set the parallelism to 1: no improvement
• [x] Set memory limits: no improvement
• [x] Disable caching: no improvement
• [x] use --output=type=docker: no improvement
• [ ] #699
• [x] Minimize the number of layers created by the Dockerfile

[EveningStarlight]

Splitting up dockerbits into separate layers does not help compile the layers.

mid-sas image builds

final sas image still has tame failure issue.