[llvm] OrcV2: also set COFF flag overrides when custom linking layer is used (PR #129533)

[Wenzel Jakob via llvm-commits]

wjakob wrote:

@lhames: I incorporated the feedback but left in the `COFF` check, which was missing in your snippet (which I assume was unintentional).

https://github.com/llvm/llvm-project/pull/129533