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

[Lang Hames via llvm-commits]

lhames wrote:

Alternatively we could expose an API that allows you to merge simple `LinkGraphs` directly into a flat buffer, then we expose the existing `SectCreate` utility that allows you to add buffers directly to the JIT with a given set of permissions and associated symbols. (This wouldn't let you control its final load address though)

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