[llvm] [Runtimes][CMake] Add CMake option to enable execute-only code generation on AArch64 (PR #143698)

[Csanád Hajdú via llvm-commits]

Il-Capitano wrote:

Thanks for taking a look, and approving this PR!

I've rebased to current main to make sure everything works, and I'll merge this at the end of the week.

https://github.com/llvm/llvm-project/pull/143698