cmake: Move to a more modern cmake version
cmake: Move to a more modern cmake version

CMake 3.12 is a good modern version to help us with the build system

Signed-off-by: Patrick José Pereira <c2b7559029b4032a4ce95718d7d3bc36c8a1d7c1@gmail.com>

Hunter522/qgroundcontrol,Hunter522/qgroundcontrol,Hunter522/qgroundcontrol,Hunter522/qgroundcontrol,Hunter522/qgroundcontrol,Hunter522/qgroundcontrol