Fixed linking issue

GF-1142
Resolved linking with pbnjson_c and pbnjson_cpp libs
via define additional path to <staging>/lib

Open-webOS-DCO-1.0-Signed-off-by: Igor Kuksyuk <ikuksyuk@luxoft.com>

Change-Id: I1108c2c3e1c03263e75ed789c3c86d827ab2e0d5