anchor.diff:  
     cmakeFlags = [
       "-DBUILD_GUI=${if withGUI then "ON" else "OFF"}"
  +    "-DSYSTEM_FFTW=ON"
       "-DSYSTEM_FMT=ON"
       "-DSYSTEM_LIBSNDFILE=ON"
  +    "-DSYSTEM_RTMIDI=ON"
  +    "-DSYSTEM_SDL2=ON"
       "-DSYSTEM_ZLIB=ON"
  -    "-DSYSTEM_SDL2=ON"
       "-DWITH_JACK=${if withJACK then "ON" else "OFF"}"
       "-DWARNINGS_ARE_ERRORS=ON"
     ];
  
positive.code:   ];
  
    buildInputs = [
      fmt_8
      libsndfile
      SDL2
      zlib
    ] ++ lib.optionals withJACK [
  
negative.code: , cmake
  , pkg-config
  , makeWrapper
  , fftw
  , fmt_8
  , libsndfile
  , rtmidi
  , SDL2
  , zlib
  , withJACK ? stdenv.hostPlatform.isUnix
  