cross compile failed in mips64el

[RickSKy]

error: failed to run custom build command for `ring v0.16.20`

Caused by:
  process didn't exit successfully: `/home/test/target/release/build/ring-28f1f805314ae446/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /home/test/.cargo/registry/src/mirrors.tuna.tsinghua.edu.cn-df7c3c540f42cdbd/ring-0.16.20/build.rs:358:10
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

maybe optional rusttls or nativetls will be bettre for more platform.