Disabled compilation of unit tests when WITH_TESTS is false

src/CMakeLists.txt

 ADD_SUBDIRECTORY( Python )
 ADD_SUBDIRECTORY( TNL )
 ADD_SUBDIRECTORY( Tools )
-ADD_SUBDIRECTORY( UnitTests )
\ No newline at end of file
+ADD_SUBDIRECTORY( UnitTests )

src/UnitTests/CMakeLists.txt

+if( WITH_TESTS STREQUAL "yes" )
+
 #ADD_SUBDIRECTORY( Containers )
 
 ADD_EXECUTABLE( UniquePointerTest${mpiExt}${debugExt} ${headers} UniquePointerTest.cpp )
@@ -37,3 +39,5 @@ ADD_TEST( StringTest${mpiExt}${debugExt} ${EXECUTABLE_OUTPUT_PATH}/StringTest${m
 ADD_TEST( ListTest${mpiExt}${debugExt} ${EXECUTABLE_OUTPUT_PATH}/ListTest${mpiExt}${debugExt} )
 ADD_TEST( ObjectTest${mpiExt}${debugExt} ${EXECUTABLE_OUTPUT_PATH}/ObjectTest${mpiExt}${debugExt} )
 ADD_TEST( UniquePointerTest${mpiExt}${debugExt} ${EXECUTABLE_OUTPUT_PATH}/UniquePointerTest${mpiExt}${debugExt} )
+
+endif( WITH_TESTS STREQUAL "yes" )