cmd/link: add Cortex-A53 erratum 843419 workaround for arm64

[luizgre]

On Cortex-A53, an ADRP instruction at page offset 0xFF8 or 0xFFC followed by a specific load/store sequence may compute an incorrect address (ARM erratum 843419). The Go internal linker had no workaround for this, while GNU ld and LLVM lld fix it by default.

During the trampoline pass, check ADRP relocations at dangerous page offsets against the erratum pattern (ported from lld's AArch64ErrataFix.cpp). When matched, redirect the ADRP+op pair through a veneer at a safe 16-byte aligned address.

Fixes #78577

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• go on master (change 764141)

To reproduce, try gomote repro 8685059658365207009.

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