[lld] [LLD][AArch64][ARM] Delay adding long thunk mapping symbols (PR #116975)

[Peter Smith via llvm-commits]

smithp35 wrote:

This removes the FIXME in the newly added aarch64-thunk-bti-multipass.s test. I've updated all the Arm thunks that have additional mapping symbols using the same pattern. I've not written any additional tests for all the Arm as these are quite difficult to write. I can add tests for some or all of these if necessary.

https://github.com/llvm/llvm-project/pull/116975