Extend COMPOSER_ARGS with --no-scripts

[boesing]

Feature Request

Q	A
New Feature	yes
BC Break	maybe

Summary

In mezzio/mezzio-skeleton#54 we found out, that the project is not tested at all. This is due to the fact that it provides pre-install-cmd script to interact with a potential user when using composer create-project.
After the project finishes up installing the user-requested packages, it cleans-up the project which also removes the unit tests which are related to the component (as it is not needed in created projects).

This is due to the fact, that composer does not pass --no-scripts when composer install (e.g.) is being executed.

I would like to request either to add --no-scripts to the COMPOSER_ARGS or to add a way to provide additional (or exclusive) COMPOSER_ARGS to the JOB which overrule the existing COMPOSER_ARGS.

Feedback is very welcome.