Can you elaborate on what you mean by "`./configure` manages to do this"?  When I was adapting this PR for Windows, I noticed that quite a few (I thought all, but perhaps not) `.dll` files were put into `$(prefix)/lib`, and then had to be manually moved to `bin` by `deps/Makefile`.  There are still some more cases where those files are being copied that can be removed if `$(libdir) = $(bindir)`, but if we shouldn't set these two variables as equivalent then I'll leave these special cases alone.

What is bad about changing `$(libdir)` on windows?  Do we actually ship static libraries?  Even `sys.dll` is placed in `$(bindir)` since it's a `.dll`, so I'm not sure what the benefit of having a separate `$(libdir)` is.