Adds a new build variable to force an update of the Docker container.
This variable can be set in a scheduled job to update the Docker image
periodically.
This way the Prefactor pipeline will keep using the latests versions of
its underlying software packages.

This command requires experimental cli to be enabled or using the
lastest Docker version. Other repositories have opted for the latter
solution so this repository follows suit.

For each of the packages that are cloned from Git it is now possible to specify a branch or tag name. Also, the list of packages installed in the "runner" build was cleaned up to reduce the size of the final container image.

[ci skip]

Former-commit-id: eccca39c
Former-commit-id: 5a824d8e
Former-commit-id: c15c47e7

Former-commit-id: bf8da57c [formerly d73065ba]
Former-commit-id: 80f16b43
Former-commit-id: 45f128cb

Former-commit-id: a1f2b822 [formerly 3360efaa]
Former-commit-id: a6c27f90
Former-commit-id: c2cdc2fb

Tammo Jan Dijkema authored 3 years ago and Marcel Loose committed 3 years ago

Former-commit-id: 5a5a5769 [formerly 634d6ea1]
Former-commit-id: c7a45be6
Former-commit-id: a04528e0

Former-commit-id: 1aa9b5f5 [formerly a176ea32]
Former-commit-id: d90a0084
Former-commit-id: 94aab794