fix: check if cmake policy is available

MotionPlanning/CMakeLists.txt

@@ -2,9 +2,9 @@ PROJECT ( Saba )
 
 CMAKE_MINIMUM_REQUIRED(VERSION 2.6.2)
 CMAKE_POLICY(VERSION 2.6)
-#if(POLICY CMP0020)
+if(POLICY CMP0020)
   cmake_policy(SET CMP0020 NEW) # qtmain add lib dependency (no effect in our case)
-#endif()
+endif()
 
 MESSAGE (STATUS "***** CONFIGURING Simox project Saba *****")