[RFC #0095] Builder should copy bom files to /layers/config/sbom

[buildpack-bot]

This issue have been automatically created from pull request buildpacks/rfcs#166.

A/C

Given for example the following file tree (at the end of buildpacks' /bin/build execution):

/layers
  /buildpack.id
    launch.bom.cdx.json
    build.bom.cdx.json
    cache-true-launch-false.toml
    cache-true-launch-false.bom.cdx.json
    /cache-true-launch-false
    cache-true-launch-true.toml
    cache-true-launch-true.bom.cdx.json
    /cache-true-launch-true

The builder should copy the bom files to create the following file tree:

/layers
  /config
    /sbom
      /launch
        /buildpack.id
          bom.cdx.json
          /cache-true-launch-true
            bom.cdx.json
      /build <- everything that is not "launch=true" should go here
        /buildpack.id
          bom.cdx.json
          /cache-true-launch-false
            bom.cdx.json
      /cache <- this is a suggested addition from https://github.com/buildpacks/lifecycle/pull/741; everything that is "cache=true" should go here
        /buildpack.id
          /cache-true-launch-true
            bom.cdx.json
          /cache-true-launch-false
            bom.cdx.json

Note that cdx could be replaced with spdx.

[natalieparellano]

Closed in #749