[lld] [lld][COFF][LTO] Implement /opt:emitllvm option (PR #66964)

[Martin Storsjö via llvm-commits]

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@@ -1822,6 +1822,8 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
         ltoDebugPM = true;
       } else if (s == "noltodebugpassmanager") {
         ltoDebugPM = false;
+      } else if (s == "emitllvm") {
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mstorsjo wrote:

> I thought about this, but the best argument I have got so far is that this matches the equivalent option for the ELF linker, where it's in the `--plugin-opt=` umbrella.

Well, `--plugin-opt=` means "plugin options". But `/opt:` in (lld-)link means "optimization options", so I don't think it's the best fit. Or can @rnk chime in here if I'm misunderstanding things?

https://github.com/llvm/llvm-project/pull/66964