ntl_jll

Hello, Currently [ntl_jll](https://github.com/JuliaPackaging/Yggdrasil/tree/master/N/ntl) only support Linux according https://github.com/JuliaPackaging/Yggdrasil/blob/acc92e78ae4d6efa90ff1a35f71cb03f628b49b7/N/ntl/build_tarballs.jl#L23-L27 It would be great to support macOS and (maybe also) Windows. Pinging @hros Best regards PS : currently working on https://github.com/s-celles/libntl-julia-wrapper and https://github.com/s-celles/LibNTL.jl/