Change request #716
Change the way features are detected
The current CMake process is to define options, check if they are applicable and set/unset depending on the system availability. This leads to issues like:
- User runs CMake
- User sees that SSL support is disabled
- User install OpenSSL
- User re-run CMake
Problem: now the option of SSL is still deactivated because it has been forced off by CMake as cache variable.
Use the DefineOption and check the availability of features before settings options.
CMake: split options and conditions, closes #716
As described in the issue, the CMake process force off a cache variable
when a condition is not met. If the user installs the requirements and
re-run CMake it must also set the variable to on which is inconvenient.
The new process is to add a secondary variable and do not touch user