Support libuv and mbedtls

[Simn]

Once HaxeFoundation/haxe#8831 lands, ocamhaxe is going to need an update to work with libuv. There are no official cygwin packages for mingw-libuv support, but I've prepared them here: https://github.com/Simn/mingw64-uv/releases

Note that even if we submit these as official packages, it's likely going to take a while before they get approved and integrated, so ocamhaxe should manually handle this for now either way.

[Simn]

This now affects both https://github.com/Simn/mingw64-uv and https://github.com/Simn/mingw64-mbedtls. It would be nice if the MinGW copy step just downloaded and untared the data here instead of requiring it to exist in the cygwin install already. Note that this could run into #14, so perhaps a check if the files exist already would be a good idea.