[clang] [compiler-rt] Reapply "[XRay][AArch64] Support -fxray-shared (#114431)" (PR #115300)

[Sebastian Kreutzer via cfe-commits]

sebastiankreutzer wrote:

@felipepiovezan @juliannagele @MaskRay Could one of you merge this, if it looks good to you?

Buildkite seems to be broken at the moment, but it works locally for me (cross-compiled with Apple toolchain). 

https://github.com/llvm/llvm-project/pull/115300