add scarthgap branch

[zach-welch-aquabyte]

Overview

This branch provides support for scarthgap, building on various required changes included in the mickledore branch.

In addition, the fossa-cli recipe was rewritten to support both native and target versions of the CLI, eliminate redundancies, and otherwise follow current best practices for writing BitBake recipes.

Acceptance criteria

1. The native CLI is used to automate image scanning with scarthgap builds.
2. The CLI can be included in images for x86-64 and ARM64 targets.

Testing plan

1. BitBake can build and package both fossa-cli and fossa-cli-native successfully.
2. The native package can be used to perform a scan and upload the results.

Automated testing is not implemented previously, so no such tests were added.

Risks

The recipe should build on all recent Yocto releases (kirkstone or newer), but I only have tested scarthgap.

Checklist

• I added tests for this PR's change (or explained in the PR description why tests don't make sense).
• If this PR introduced a user-visible change, I have updated relevant documentation.

[cmboling]

@zlav hey hey, is this ready to merge?