[llvm] [JITLink][XCOFF] Setup initial build support for XCOFF (PR #127266)

[Hubert Tong via llvm-commits]

hubert-reinterpretcast wrote:

> It's in the roadmap but it is not the top priority. I'd like to support all the features and relocations implement first, and worry about things like the static initializers and such after.

Can you give me an answer as to how JITLink fits into BOLT? I am trying to emphasize that the particular usage of JITLink for the purposes of BOLT can have additional complications in the context of AIX (which is not directly tied to XCOFF, but extends to additional linker behaviours).

https://github.com/llvm/llvm-project/pull/127266