refactor: streamline ephemeral GPG key generation and signing process

[alexlovelltroy]

This pull request updates the RPM build GitHub Actions workflow to improve security and automation by switching to ephemeral GPG keys for signing and modernizing variable usage and output handling. The changes eliminate the need for long-lived signing credentials and streamline the build and release process.

Security and GPG Key Management:

• Replaces importing a static GPG private key with generating an ephemeral GPG key for each build using the OpenCHAMI/gpg-signing-manager action. The ephemeral key is configured with a 1-day expiration and unique metadata per run. [1] [2]
• Updates all signing steps (source tarball and RPMs) to use the ephemeral key's fingerprint, removing dependencies on static secrets and passphrases.
• Adds a step to export the ephemeral public key for distribution, replacing the previous export of a static public key. [1] [2]

Workflow Modernization and Output Handling:

• Refactors output variable usage to use the new GITHUB_OUTPUT mechanism instead of deprecated set-output, and consistently uses the dynamically determined version from the get_version step. [1] [2]
• Updates conditional steps and asset naming to reference the dynamically determined version, ensuring consistency throughout the workflow.

Build Process Improvements:

• Simplifies the source tarball creation by removing unnecessary transformations and using the correct version variable.

These changes increase the security of the RPM build pipeline and align the workflow with current GitHub Actions best practices.

[synackd]

I might be missing something, but I don't see gpg-ephemeral-key used here. Was that intentional?

[alexlovelltroy]

It is using parts from the gpg signing machinery. At this point, it is not doing ephemeral keys and is instead signing with the repo key. See build-rpm.yaml:

• Lines 37-48
• Lines 77-80
• Lines 99-103

[synackd]

At this point, it is not doing ephemeral keys and is instead signing with the repo key.

Got it, just wanted to make sure.

This looks reasonable to me. Just one comment below.