build-script: T3664: Added flavor name to a target file name (backport #616)

[mergify]

Change Summary

Added flavor name to a target file name

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

• https://vyos.dev/T3664

Component(s) name

build-script

Proposed changes

Mark artifacts with a flavor name for better clarity.

How to test

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

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This is an automatic backport of pull request #616 done by [Mergify](https://mergify.com).