faulty basedir does not always error properly in windows

faulty basedir does not always produce error properly in windows, because when the dirs are sliced down the final path has an improper prefix resulting in paths like "C:node_modules\module\transform.js" (notice missing slash), which, at least in my case, causes it to attempt to resolve "node_modules\..." relative to the cwd.  this sometimes will actually succeed causing havoc down the line instead of erroring as it should.  see added test for more clarity