Multiarch image build needs to check the requested platforms are supported

[mkolesnik]

I had a problem when building nettest multiarch image, which was non-trivial to pinpoint to platform support.

The image build script should have a check that buildx supports all requested platforms, and if not point to (or suggest) a solution.

To see supported platforms use docker buildx ls and look at the platforms (there might be a more specific command)

e.g. arm64 not supported:

$ docker buildx ls
NAME/NODE         DRIVER/ENDPOINT             STATUS  PLATFORMS
buildx_builder *  docker-container                    
  buildx_builder0 unix:///var/run/docker.sock running linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/386
default           docker                              
  default         default                     running linux/amd64, linux/386

with arm64 (and others) supported:

$ docker buildx ls
NAME/NODE         DRIVER/ENDPOINT             STATUS  PLATFORMS
buildx_builder *  docker-container                    
  buildx_builder0 unix:///var/run/docker.sock running linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/386, linux/arm64, linux/riscv64, linux/ppc64le, linux/s390x, linux/mips64le, linux/mips64
default           docker                              
  default         default                     running linux/amd64, linux/386, linux/arm64, linux/riscv64, linux/ppc64le, linux/s390x, linux/arm/v7, linux/arm/v6

[stale]

This issue has been automatically marked as stale because it has not had activity for 60 days. It will be closed if no further activity occurs. Please make a comment if this issue/pr is still valid. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had activity for 60 days. It will be closed if no further activity occurs. Please make a comment if this issue/pr is still valid. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had activity for 60 days. It will be closed if no further activity occurs. Please make a comment if this issue/pr is still valid. Thank you for your contributions.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further
activity occurs. Thank you for your contributions.