[llvm] reland [InlineAsm] wrap ConstraintCode in enum class NFC (PR #66264)

[Reid Kleckner via llvm-commits]

https://github.com/rnk approved this pull request.

Looks good, I spot checked the Mips and SystemZ issues I saw locally. I think some stuff just got lost in your rebase attempt. I see the buildkite checks on Linux passed on this PR and the previous one.

https://github.com/llvm/llvm-project/pull/66264