Enhancement of cpp header-only-library sample

[Brenne]

Removing the static library from the outgoing config, disabling CppCompile and CreateStaticLibrary tasks

Context

Benefit of this solution is that no unnecessary static library is created and neither a dummy source. In addition the changes result in increased performance because unnecessary tasks are disabled.

https://github.com/gradle/gradle-native/issues/1074

Contributor Checklist

• [x] Review Contribution Guidelines
• [x] Make sure that all commmits are signed off to indicate that you agree to the terms of Developer Certificate of Origin.
• [x] Check "Allow edit from maintainers" option in pull request so that additional changes can be pushed by Gradle team
• [ ] Ensure that tests pass locally: ./gradlew check (on my setup 3 tests in master fail, the same tests still fail)