[Development] How to create dummy plugins in qtbase?

[Oswald Buddenhagen]

On Sun, Oct 28, 2018 at 01:59:07PM -0400, Kyle Edwards wrote:
>    However, I'm not sure how to create a new Qt module that's visible
>    to the tests without also being installed/visible outside the
>    tests.
>
that's an unsolved problem.
qtmultimedia/tests/auto/unit/qmediaserviceprovider also just installs
them "for real".