[clang] [flang] [llvm] [flang] Add runtime trampoline pool for W^X compliance (PR #183108)

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https://github.com/jeanPerier approved this pull request.

Looks great, thanks for the work.
As I mentioned inside the patch, this will not work when combined with MLIR inlining (experimental in flang) because of the difficulty of finding the place to create and destroy the trampolines, but I think an IR and lowering modification is needed to solve this.

https://github.com/llvm/llvm-project/pull/183108