tests: add a "missing" tests for manifest content in test-racy-mutations.t Trying to figure out why the divergence in behavior on Windows. The first test shows everything is the same on all platforms; the second shows that the other #testcase also diverges. The difference might be that `00manifest.i` doesn't get updated (and copied over) after `pre-race` is created, but I've no idea why that would be either.