Enabling build scripts for Windows

[jd-foster]

I've been working on "porting" the Windows specific logic in the build scripts from BLIS to the configure and Makefile to their equivalent in libflame (diffs are here: https://github.com/JuliaPackaging/Yggdrasil/pull/8671/files)

It's a work in progress (still requires testing the binaries), but was wondering if this would be of interest as a PR to upstream here? Would someone be willing to review it?

As an extra, there is also a fix for #100 when linking while building for macOS.