CMake: Build shared libraries by default
CMake: Build shared libraries by default

This is also what other projects are doing.

FSMaxB/cJSON,gatzka/cJSON,kbranigan/cJSON,FSMaxB/cJSON,DaveGamble/cJSON,etodd/cJSON,DaveGamble/cJSON,gatzka/cJSON,FSMaxB/cJSON,DaveGamble/cJSON,gatzka/cJSON,gatzka/cJSON,FSMaxB/cJSON,gatzka/cJSON,FSMaxB/cJSON,DaveGamble/cJSON