[llvm] llvm: Add missing `LLVM_ABI` annotations (PR #171629)

[Nikita Popov via llvm-commits]

================
@@ -25,11 +25,12 @@ enum class KCFIHashAlgorithm { xxHash64, FNV1a };
 KCFIHashAlgorithm parseKCFIHashAlgorithm(StringRef Name);
----------------
nikic wrote:

At least for the time being, we should annotate everything.

(At some point we may decide not to export some things, but those are going to need explicit annotations along the line of LLVM_NOT_ABI to play well with ids.)

https://github.com/llvm/llvm-project/pull/171629