Fix some unaligned reads on SPARC in LTO

[dhduvall]

This fixes #43593 by eliminating some undefined behavior.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @pnkfelix (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[aidanhs]

Thanks for the PR @dhduvall! We'll check in now and again to make sure @pnkfelix or another reviewer gets to this soon.

[nagisa]

@bors r+

[bors]

📌 Commit e412cb3 has been approved by nagisa

[nagisa]

Thanks for the fix!

[bors]

⌛ Testing commit e412cb3 with merge 9b6c238...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: nagisa
Pushing 9b6c238 to master...