In order to have objects like readanysf~ and purest_json work on Windows, they need to include DLLs for libraries like ffmpeg and curl. In order for the DLLs of the objects to load other DLLs from that same folder, SetDllDirectory() needs to be set first. This requires a minimum of Windows XP SP1 (10 years old at this point).
There are three patches included, the first sets up the new build system for this, the second sets up makefile.mingw for this. The third is the actual change to s_loader.c. I think MSVC sets WINVER automatically, but just be sure its set to 0x0502 for this to work.