Great. Thanks again for checking. The new version will be uploaded soon to the official entry. And I've upped the Window size.
And the main problem with libffi is more configuring it all such that your SBCL is able to run gcc, pkg-config, et all in the right environment (mingw).
Actually, if you run SBCL from within a MinGW window it -should- all work. Though I'd be a little worried about getting `/msys/style/paths/`