Install targets and files in default Runtime and Development CMake
components to determine files included in the two Debian packages.
Move to CMake minimum version to 3.12 to allow using NAMELINK_COMPONENT
option in install() allowing adding .so files in a separate component,
Developement here.
Use CPack to build the two Debian packages.

Co-authored-by: Lucino772 <lucapalmi772@gmail.com>

Consider the ful package delivers the two libraries wiringPi and
wiringPiDev with the associated binary gpio. We don't have to build and
install each component separately first.

By the way, set SOVERSION to version major. It also fixes wiringPiDev
shared library version not correctly set.

Building position independant code is the default behavior for CMake
when compiling shared library targets.