BUG: 14033 Fix cmake configuration error with CMake 2.8.10.2

The variable was accumulating some garbage values. Cleaned that up.

Change-Id: I09d98d5c4dfa085739c39faa74aebe8ecffa0bcb
Merge topic 'fix_cmake_2.8.10_plugins_issue' into next

ecbeaa1 BUG: 14033 Fix cmake configuration error with CMake 2.8.10.2