fastfetch uses cmake for building. pkg-config is recommended for better library detection. The simplest steps to build the fastfetch and flashfetch binaries are:

mkdir -p build
cd build
cmake ..
cmake --build . --target fastfetch

If the build process fails to find the headers for a library listed in dependencies, fastfetch will simply build without support for that specific feature. This means, it won't look for it at runtime and just act like it isn't available.

Currently GCC or clang is required (MSVC is not supported). MSYS2 with CLANG64 subsystem (or CLANGARM64 if needed) is suggested (and tested) to build fastfetch.

1. Install MSYS2
2. Open MSYS2 / CLANG64 (not MSYS2 / MSYS, which targets cygwin C runtime)
3. Install dependencies

pacman -Syu mingw-w64-clang-x86_64-cmake mingw-w64-clang-x86_64-pkgconf mingw-w64-clang-x86_64-clang mingw-w64-clang-x86_64-vulkan-loader mingw-w64-clang-x86_64-vulkan-headers mingw-w64-clang-x86_64-opencl-icd mingw-w64-clang-x86_64-cppwinrt

Follow the building instructions of Linux next.