Implement test to detect non-open source licenses

[MichaelSimons]

This is related to #2359. Source-build should have it's own test to catch/prevent non-open source licensed code.

[MichaelSimons]

[Triage] This is not a trivial task. There are a lot of intricacies in scanning for non-permissive licenses and the scanning itself will be time intensive.

From @omajid: Existing tools to scan: https://github.com/nexB/scancode-toolkit

[omajid]

Debian has some recommendations too https://wiki.debian.org/CopyrightReviewTools