core:  flb_scheduler fix for macOS
src/flb_scheduler.c: cosumer_bytes() gives errors in macOS (10.13,... ?).
function flb_pipe_r can return value 0 if is considered as error.
This patch allows return value zero.
@@ -44,7 +44,11 @@ static inline int consume_byte(flb_pipefd_t fd)
/* We need to consume the byte */
ret = flb_pipe_r(fd, &val, sizeof(val));
+#ifdef __APPLE__
+ if (ret < 0) {
+#else
if (ret <= 0) {
+#endif
flb_errno();
return -1;
}
