showcase: old files not deleted from 'latest' folder causing some files not be overwritten by the new ones

[christophercr]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[X] Bug report  
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#got-a-question-or-problem

Current behavior

Not all the new content is copied to the latest folder. This happens when the new files have exactly the same name and size as the old ones i.e. the index.html file. This causes the Showcase to be completely broken and not loading at all due to wrong references to JS files.
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Expected behavior

The deployed Showcase under the latest on GhPages should work correctly after every release.

Minimal reproduction of the problem with instructions

Open the latest version of the Showcase: https://stark.nbb.be

What is the motivation / use case for changing the behavior?

Fully working Showcase app.

Environment

Stark version: 10.0.0-beta.4