[llvm] [DTLTO] Add remote compiler option forwarding coverage (PR #208589)

[Edd Dawson via llvm-commits]

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@@ -0,0 +1,90 @@
+REQUIRES: ld.lld
+
+## Check that DTLTO serializes LTO configuration state into the remote Clang
+## command line.
----------------
playstation-edd wrote:

```suggestion
## Check that DTLTO passes LTO configuration to the remote Clang
## via the command line.
```

Please consider this optional/opinion. 

While I think it's fair to describe the option passing as a means of serialization, IMO it does require a degree of squinting. They weren't designed for serialization and so the framing seems unusual. There's also discussion of first-class serialization of LTO configuration state on https://discourse.llvm.org/t/synchronizing-lto-code-generation-configuration-between-clang-and-lld-dtlto/91276 so I suggest steering away from that language, to avoid future crossing of wires.

https://github.com/llvm/llvm-project/pull/208589