cmake HAVE_FFTW examples

snl-dakota/dakota cmake/DakotaOptions.cmake :199 

option(HAVE_FFTW "Find and use an installed fftw package. This OPTION has no
  effect if HAVE_FFT is OFF" OFF)

snl-dakota/dakota cmake/FftwExternalProject.cmake :38 

endif(HAVE_FFTW)

hlrs-vis/covise cmake/Using/UseFFTW.cmake :10 

ADD_DEFINITIONS(-DHAVE_FFTW)