Add position independent code feature to CMakeList.txt

Enable Position Independent Code for shared lib

src/lib_json/CMakeLists.txt

diff --git a/src/lib_json/CMakeLists.txt b/src/lib_json/CMakeLists.txt
index 9730e9a..d0d717f 100644
--- a/src/lib_json/CMakeLists.txt
+++ b/src/lib_json/CMakeLists.txt
@@ -73,6 +73,7 @@
     SET_TARGET_PROPERTIES( jsoncpp_lib PROPERTIES VERSION ${JSONCPP_VERSION} SOVERSION ${JSONCPP_SOVERSION})
     SET_TARGET_PROPERTIES( jsoncpp_lib PROPERTIES OUTPUT_NAME jsoncpp
                            DEBUG_OUTPUT_NAME jsoncpp${DEBUG_LIBNAME_SUFFIX} )
+    SET_TARGET_PROPERTIES( jsoncpp_lib PROPERTIES POSITION_INDEPENDENT_CODE ON)
 
     # Set library's runtime search path on OSX
     IF(APPLE)