Add CMake project config files

[jynik]

CMake project config files help users of libbladeRF to locate it at configuration time via CMake.

We should be neighborly and provide these.

Examples from the SoapySDR Project:

• SoapySDR *Config.cmake items
• Installation of the above files

[polygon]

I made something like that a while ago. Maybe it helps as a starter. https://gist.github.com/polygon/61e33a0fccecaf4ecf7a

Usage as normal via

find_package(LibbladeRF)
if (NOT LIBBLADERF_FOUND)
  message("libbladeRF not found")
else ()
  message(STATUS "Using libbladeRF from " ${LIBBLADERF_INCLUDE_DIRS})
  include_directories(${LIBBLADERF_INCLUDE_DIRS})
endif ()

[jynik]

@guruofquality At a minimum, I'd like to install a FindLibbladeRF.cmake, if you'd allow for me to pull that into the project from SoapyBladeRF -- as you noted way back when, these are things we should really be providing to library users.

[guruofquality]

@jynik sure you can knab the file https://github.com/pothosware/SoapyBladeRF/blob/master/FindLibbladeRF.cmake

But if you are going to do the cmake project files, we can totally drop the FindLibbladeRF.cmake and having people copy it into their projects. I might suggest a more cut-down project to copy from than SoapySDR:

muparserx:

• https://github.com/beltoforion/muparserx/tree/master/cmake
• https://github.com/beltoforion/muparserx/blob/master/CMakeLists.txt#L87

spuce:

• https://github.com/audiofilter/spuce/tree/master/cmake
• https://github.com/audiofilter/spuce/blob/master/CMakeLists.txt#L55

Theres usually more than one way to do this, but the above stuff is pretty formulaic, 2 short files, and its worked so far across a wide range of cmakes going back to whatever is on 12.04 ubuntu.

[cwozny]

Any ability for Nuand to add this capability? Seems like a light enough lift. Would love to just be able to have CMake find the package for me.