[compiler-rt] [compiler-rt] Add CMake option to enable execute-only code generation on AArch64 (PR #140555)

[Csanád Hajdú via llvm-commits]

Il-Capitano wrote:

@petrhosek Should I change the CMake option name to `RUNTIMES_EXECUTE_ONLY_CODE` then?
My only hold-up is that I couldn't find any examples of this naming convention in current main, but if this is the agreed upon naming scheme for new flags I'm happy to make that change.

https://github.com/llvm/llvm-project/pull/140555