adds libzstd_linux_riscv64.a build

[denisgolius]

This PR will add:

1. riscv64 architecture support by adding native zstd lib.
2. Update zig builder docker image to the latest stable zig version in docker which is 0.13.0 , see Check my updated fork euantorano/docker-zig#3

[denisgolius]

cc @f41gh7