About ensuring that `KokkosFFT_ENABLE_HOST_AND_DEVICE` is enabled

[tpadioleau]

If a project relies on the option KokkosFFT_ENABLE_HOST_AND_DEVICE, it will likely need to know if the installed KokkosFFT provides it or not.

Could adding #cmakedefine KOKKOSFFT_ENABLE_HOST_AND_DEVICE do the job ?

cc @jbigot

[yasahi-hpc]

Makes sense. Can you wait for v0.3.0?

[tpadioleau]

yes it is fine for me

[jbigot]

I was thinking of offering support for the COMPONENTS keyword of find_package so that the requirement can be expressed from CMake and in case multiple versions are installed, the right one is found