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

[Peter Klausler via cfe-commits]

klausler wrote:

One last minor point: the commit message talks about `W^X` compliance, but it's really about `!(W&X)`.  `W^X` can be zero so long as both W and X are.

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