cmake HAS_FFTW3 examples

mcallegari/qlcplus engine/audio/src/CMakeLists.txt :86 

target_compile_definitions(${module_name} PUBLIC
        HAS_FFTW3
    )

mcallegari/qlcplus engine/src/CMakeLists.txt :180 

target_compile_definitions(${module_name} PUBLIC
        HAS_FFTW3
    )

d1vanov/Simple-FFT CMakeLists.txt :172 

add_definitions("-DHAS_FFTW3")