helper : add proper RPATH to binary, fixes #379

This was causing an issue for helper usage on linux, see #379.
This patch was confirmed to fix it.

src/tools/helper/CMakeLists.txt

@@ -15,6 +15,7 @@ add_executable(${HELPER_TARGET} WIN32
 target_link_libraries(${HELPER_TARGET} ${Qt5Core_LIBRARIES} ${Qt5Network_LIBRARIES} qslog shared)
 std_target_properties(${HELPER_TARGET})
 set_target_properties(${HELPER_TARGET} PROPERTIES
+  INSTALL_RPATH "${QTROOT}/lib"
   OUTPUT_NAME ${HELPER_NAME}
 )