[llvm] [Support] Make readNext default to unaligned (PR #88808)

[Fangrui Song via llvm-commits]

MaskRay wrote:

This is like how to we define `packed` in llvm/include/llvm/Object/ELFTypes.h. We just assume everything can be unaligned.

There should be no codegen difference to aarch64/x86/ppc64, but certain 32-bit architectures and riscv64 -mstrict-align will have some penalty.

https://github.com/llvm/llvm-project/pull/88808