vitis backend tarball fix

[calad0i]

A# Description

As the current vitis writer only overwrites the headers in nnet_utils after calling the vivado_writer, the tarball produced is with vivado configurations. This PR overrides the tarball generated also.

(Though, do we need to keep the tarball?)

Type of change

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Note: Please delete options that are not relevant.

• Bug fix (non-breaking change that fixes an issue)

Tests

Checklist

• I have read the guidelines for contributing.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have installed and run pre-commit on the files I edited or added.
• I have added tests that prove my fix is effective or that my feature works.

[jmitrevs]

Did you look at the new tarball to make sure it makes sense?

[calad0i]

Did you look at the new tarball to make sure it makes sense?

Ran a few vitis synths on the generated tarballs (the ones shown in #973). All finished without issue.