Adding FFTW3 for g'mic-qt?

I was trying to compile g’mic-qt to work with gmic-sharp. To do that I have to install FFTW3 on windows. How exactly am I suppose to add FFTW3 into window so that g’mic-qt can actually build?

To compile gmic and gmic-qt, we use the toolchain provided by MSYS2. It provides pacman, a package manager that is able to install libfftw3, as well as all other dependencies required to compile gmic-qt.
MSYS2 is really great for this.

I stopped building stuff 1.5 decades ago because it is such a bother and good builds are ubiquitous. I was going to suggest cross-compiling in a Linux environment but then C Sharp is a Windows thing isn’t it.