Updated CMakeList.txt to support multiple targets (gravity cli, gravityapi shared lib and gravityapi static lib). Tested Windows(VC2019, MinGW64), Ubuntu 18.04 (gcc)
Updated CMakeList.txt to support multiple targets (gravity cli, gravityapi shared lib and gravityapi static lib). Tested Windows(VC2019, MinGW64), Ubuntu 18.04 (gcc)

marcobambini/gravity,marcobambini/gravity,marcobambini/gravity