child_process: collectOutputWindows handle broken_pipe from ReadFile
child_process: collectOutputWindows handle broken_pipe from ReadFile

This was found on a user's machine when calling "git" as a child process from msys.  Instead of getting BROKEN_PIPE on GetOverlappedREsult, it would occur on ReadFile which would then cause the function to hang because the async operation was never started.

andrewrk/zig,andrewrk/zig