Better error logging

What does this MR do?

• Expose the flawfinder errors when it fails to run (!51 (merged))
• Output help text if a character encoding issue is encountered (!51 (merged))

What are the relevant issue numbers?

gitlab-org/gitlab#7020 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• [-] Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• [-] Tests added for this feature/bug
• [-] Job definition updated, if necessary
  • [-] Auto-DevOps template
  • [-] Job definition example
  • [-] CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer

Screenshot