Fixed by falling back to using 'waitpid' instead of 'waitid'.

BUG=http://code.google.com/p/v8/issues/detail?id=401

Review URL: http://codereview.chromium.org/149450

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2424 ce2b1a6d-e550-0410-aec6-3dcde31c8c00