[lld] [codex] [lld][COFF] Emit ThinLTO indexes for unused lazy bitcode (PR #203321)

[David Zbarsky via llvm-commits]

dzbarsky wrote:

@cjacek I think you've been touching this recently, I'm unfamiliar with this code but it seems reasonable and solves the issue I was hitting, WDYT?

https://github.com/llvm/llvm-project/pull/203321