r70188 made it possible to run old-run-webkit-tests using Win32 Perl (once you remove an early bailout in that script). But when you do so, DumpRenderTree hangs while calling fflush(), which obviously makes it unusable.
I tried replacing old-run-webkit-test's use of O_NONBLOCK with IO::Select. This works fine on Cygwin, but ORWT thinks that every test is timing out immediately. The problem seems to be that IO::Select only works with sockets on Windows.