This mimics behaviour of jest - if you want to use projects,
you need to pass the config by file. This teaches stryker to do
the same - if you set explicit config path in jest config,
that gets passed into jest and voila, multi project jest works :)

https://github.com/swist/stryker-test is the minimum reproducible
example repo for this

Turns out that we can also make projects play nice with stryker-modified jest configs. There are two requirements however - they need to have rootDir set in jest CLI args and we need to make sure that the filename ends in .json so that require doesn't trip over