ibmi: return 0 from uv_resident_set_memory()

PR-URL: https://github.com/libuv/libuv/pull/1939
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

src/unix/ibmi.c

@@ -72,7 +72,8 @@ void uv_loadavg(double avg[3]) {
 
 
 int uv_resident_set_memory(size_t* rss) {
-  return UV_ENOSYS;
+  *rss = 0;
+  return 0;
 }