[lld] [llvm] [LLD][AArch64] Make adrp+ldr relaxation per-symbol all-or-nothing (PR #208396)

[Peter Smith via llvm-commits]

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smithp35 wrote:

If I've read the original code correctly, the existence of one non-pair would prevent relaxation for the whole section. Whereas that decision is now made per symbol.

Perhaps change to
`## Relocations to symbol do not appear in pairs, no relaxations should be applied for that symbol.`

Could be worth adding a paired relocation to a different symbol that can be relaxed to show the difference.

https://github.com/llvm/llvm-project/pull/208396