install_helpers: add ldconfig step to install_ndncxx

refs #3073

Change-Id: I51fb6f34bb5a6bb1a42a2f0807a8cb0548a2dc4c
diff --git a/install_helpers/install_ndncxx.py b/install_helpers/install_ndncxx.py
index 150870c..94850be 100644
--- a/install_helpers/install_ndncxx.py
+++ b/install_helpers/install_ndncxx.py
@@ -12,4 +12,5 @@
     os.system("./waf -j1")
     os.system("sudo ./waf install")
     os.system("mkdir -p ~/.ndn")
+    os.system("sudo ldconfig")
     os.chdir("..")