[lld] [lld][MachO] Add --lto-obj-path for distributed ThinLTO (PR #203365)

[David Zbarsky via llvm-commits]

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dzbarsky wrote:

ah it's the opposite way - bazel output are declared statically, so it will declare an output for the single `ltoObjPath` so that's the one we must be sure to write. If any other ones are written, bazel will not know about them and ignore them. But yes it will also pass `--thinlto-index-only` so I think it's fine as is!

https://github.com/llvm/llvm-project/pull/203365