Refactor HackRF build system with a more modern CMake style.
Install files to allow library users using CMake to
find_project(HackRF CONFIG) and obtain HackRF::hackrf
and/or HackRF::hackrf_static library targets.
Add options ENABLE_STATIC_LIB and ENABLE_SHARED_LIB
to allow shared or static library to be disabled.
(Default builds both shared and static libraries.)
Add option ENABLE_HACKRF_SWEEP, when disabled allows
building without FFT library. (Default enabled.)
Add option DISABLE_USB_DEVICE_DISCOVERY for a compile definition
which could be used to alter libusb usage as needed on Android.
