Re enable riscv ci

[yuzibo]

No description provided.

[rustbot]

⚠️ Warning ⚠️

• The following commits have merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged.

  • 4c98310

  You can start a rebase with the following commands:

  $ # rebase
  $ git pull --rebase https://github.com/rust-lang/compiler-builtins.git main
  $ git push --force-with-lease
  

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.