Add distortosSetFixedConfiguration() to distortos-utilities.cmake
Add distortosSetFixedConfiguration() to distortos-utilities.cmake

This is very similar to distortosSetConfiguration(), but the variables
are not stored in cache, not saved in distortosConfiguration.cmake file
and not presented in the GUI. This is basically meant to define fixed
values which will be inserted into generated distortosConfiguration.h
file.
DISTORTEC/distortos,DISTORTEC/distortos,DISTORTEC/distortos,DISTORTEC/distortos