Migrate build file from Groovy to Kotlin DSL of samples-composite project

[Stexxe]

Fixes #1161

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I confirm that I have read the Contributor Agreements v1.0, agree to be bound on them and confirm that my contribution is compliant.

[robstoll]

@Stexxe thanks for your first contribution to Atrium 🙂 👍

Please, next time, add the comment I'll work on this to the corresponding issue before you start working on it. There was already someone else working on it which is kind of a pity. Anyway... how about a next one?
https://github.com/robstoll/atrium/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22

[Stexxe]

@robstoll, I don't disturb someone else's work, and it's up to you to decide to merge my pull request or to wait for another one. I don't like to comment like this because, in the end, I may not finish it, so in my opinion, it's better to just deliver a solution, especially for small tasks like this one. I can write I'll work on this just before I create a PR if you want.

[robstoll]

@Stexxe I see your point. Would be good if you could write a comment, only this way I can assign the issue to you. You might want to do this also for #1161 so that I can assign it to you