ci: add Linux ARM64 release binary

[yanghang8612]

Summary

• build the static Linux ARM64 binary on GitHub's ubuntu-24.04-arm runner
• cache and gather solc-static-linux-arm with the existing release binaries
• add the ARM64 binary to both release tarballs and upload it to S3
• publish the solc-bin-compatible path linux-arm64/solc-linux-arm64-v<version>

Why

Upstream Solidity v0.8.31 added a Linux ARM64 release asset. The GitHub build workflow needs the same artifact so TRON's v0.8.31 release output remains aligned with upstream.

Validation

• parsed .github/workflows/build.yml as YAML
• verified upload-to-s3 depends on b_linux_arm
• ran git diff --check

The production build workflow runs after merge into release_0.8.31.

[github-actions]

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