[lld] [lld][ICF] Prevent merging two sections when they point to non-globals (PR #136641)

[Peter Smith via llvm-commits]

smithp35 wrote:

> I'm traveling with limited internet access and haven't fully analyzed the scenario.
> 
> I'm concerned that enumerating relocation types adds unnecessary complexity, potentially opening a new can of worms. Coverage is poor, other architectures are not covered, and adapting to new relocation types could be challenging.

One suggestion I thought of making was to have something like a `isPartOfCompoundGOTAccess(Relocation)` which could in theory be implemented as a target specific query.

>From comments on the outliner issue, I believe that RISCV prevented the outliner from splitting apart compound sequences as it was not possible to split these across separate sections, although it is possible on AArch64.

https://github.com/llvm/llvm-project/pull/136641