[llvm] [MC] Set SHF_EXCLUDE for AArch64 (and other) build attributes sections (PR #125824)

[Hans Wennborg via llvm-commits]

zmodem wrote:

Please take a careful look since I'm not really familiar with these things. See comments on https://github.com/llvm/llvm-project/pull/123990 for background.

Note that this also affects other consumers of `emitAttributesSection()`, such as `.ARM.attributes`, `.hexagon.attributes`, and `.riscv.attributes`, but I think they also don't want the sections in the linked output?

https://github.com/llvm/llvm-project/pull/125824