The modern meaning of the construct if( NOT ON ) was added in CMake 2.8,
but when the cmake_minimum_required not set in user code and no policy
level is set in the CMake config, then CMake 2.8 features cannot be
used. In old CMake (the default), ON is interpreted as a variable, and
because it is not defined, it is considered false. The same is true of
OFF.
This change sets a variable as ON, so that old CMake interpretation is
correct, and the if works as expected regardless of policy version.
Change-Id: I67d7ed4ceaf8248eeb5a1c7f54009d72313f3f5d
Cordell Bloor
4a35f560f6