Attest build provenance

[acouvreur]

https://github.com/actions/attest-build-provenance

A verifiable signature is generated for the attestation using a short-lived Sigstore-issued signing certificate. If the repository initiating the GitHub Actions workflow is public, the public-good instance of Sigstore will be used to generate the attestation signature. If the repository is private/internal, it will use the GitHub private Sigstore instance.

Once the attestation has been created and signed, it will be uploaded to the GH attestations API and associated with the repository from which the workflow was initiated.