[clang] [llvm] [DLCov 4/5] Track coverage and origins through IRBuilder (PR #108214)

[J. Ryan Stinnett via cfe-commits]

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

This part looks good overall, thanks for working on this! 😄 

One small note inline below.

https://github.com/llvm/llvm-project/pull/108214