[os2]: Implement pipe_has_data procedure

core/os/os2/pipe_posix.odin

@@ -44,3 +44,28 @@ _pipe :: proc() -> (r, w: ^File, err: Error) {
 	return
 }
 
+@(require_results)
+_pipe_has_data :: proc(r: ^File) -> (ok: bool, err: Error) {
+	if r == nil || r.impl == nil {
+		return false, nil
+	}
+	fd := posix.FD((^File_Impl)(r.impl).fd)
+	poll_fds := []posix.pollfd {
+		posix.pollfd {
+			fd = fd,
+			events = {.IN, .HUP},
+		},
+	}
+	n := posix.poll(raw_data(poll_fds), u32(len(poll_fds)), 0)
+	if n != 1 {
+		return false, _get_platform_error()
+	}
+	pipe_events := poll_fds[0].revents
+	if pipe_events >= {.IN} {
+		return true, nil
+	}
+	if pipe_events >= {.HUP} {
+		return false, .Broken_Pipe
+	}
+	return false, nil
+}