Implementation of multi-arch support for extension packages

[pacostas]

Summary

This implementation is based on the RFC https://github.com/buildpacks/rfcs/blob/main/text/0128-multiarch-builders-and-package.md

This PR allows the pack extension package to generate multi-platform OCI images and create an image index to combine them.

It also adds the --path flag to point to a directory on the extension that needs to be packaged.

This PR has not been tested in packaging a builder with multi-platform extension.

Output

Before

• We were not able to create multi-platform extensions
• We were not able to point to the directory of the extension

After

• Can generate multi-platform OCI images by using the --target flag
• Can specify the path of where the extension is located, using the --path flag.

Documentation

• Should this change be documented?
  • Yes
  • No

Related

Resolves #2183
Resolves #2160

[jjbustamante]

@pacostas Thank you so much for this work!!! I will review it tomorrow!!!

[pacostas]

You are welcome, feel free to make any suggestions! :)

[pacostas]

@jjbustamante Hello! With respect to your time, did you have the chance to take a look on the implementation?

[jjbustamante]

@jjbustamante Hello! With respect to your time, did you have the chance to take a look on the implementation?

@pacostas I am so sorry I haven't reviewed your PR, I will be pulling it and testing it locally, also, we are evaluating the current state of Kaniko because we are not sure how it will affect us. We use Kaniko for our extension implementation.

[pacostas]

Thank you very much :)

Thank you for the information about kaniko, do you know if kaniko is used somewhere else except extension and if there is a discussion/thread about that issue (to be in the loop)?

[jjbustamante]

Thank you very much :)

Thank you for the information about kaniko, do you know if kaniko is used somewhere else except extension and if there is a discussion/thread about that issue (to be in the loop)?

We only use Kaniko for extensions, we discussed it during our Working Group meeting on December 12th, but the recording is not on Youtube 😞