Running the lit tests and the spec tests is now really great.
I was recently debugging an issue with binaryen.js tests and wished they were either in lit of using the same parallel executor as the spec tests.
Should put some effort into making all the test suites use one of these two mechanism.
Presumably converting a given test suite (e.g. binaryen.js) to use the new parallel test runner from the spec test is a much smaller job than converting it to lit (i.e. none of the individual tests would even need to be touched), so that might be good thing to do for all the test suites that don't current make sense as lit.