[llvm] [BOLT][AArch64] Relax calls and branches with fragment clusters (PR #215825)

[Alexandros Lamprineas via llvm-commits]

labrinea wrote:

The [buildkite/libcxx-ci](https://buildkite.com/llvm-project/libcxx-ci/builds/265662) and [buildkite/libcxx-ci/pipeline](https://buildkite.com/llvm-project/libcxx-ci/builds/265662#01a0d29b-54ff-43f5-8534-779f307802cf) failures are due to rewriting the commit history. Not genuine errors. I am merging this now.

https://github.com/llvm/llvm-project/pull/215825