docs: update Makefile help

[kairoaraujo]

What this PR does / why we need it

Add help messages for build and build-goreleaser

Acceptance Criteria Met

• [x] Docs changes if needed
• [ ] Testing changes if needed
• [ ] All workflow checks passing (automatically enforced)
• [ ] All review conversations resolved (automatically enforced)
• [x] DCO Sign-off

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[ChaosInTheCRD]

@kairoaraujo lgtm!