By: Tom Sydney Kerckhove <syd@cs-syd.eu>
Add --mutation-coverage-jobs to cap coverage parallelism Test suites with expensive per-test setup (e.g. tmp-postgres) can overwhelm the system when getNumCapabilities children try to start at once. Expose a knob to limit it. mutationCheck.nix gets a coverageJobs argument that, when set, passes the flag to both the first-suite and extra-suite coverage invocations.