[lld] [lld-macho][arm64] Enhance safe ICF with thunk-based deduplication (PR #106573)

[Pengying Xu via llvm-commits]

Colibrow wrote:

Since safe_thunks functionality is already implemented for Mach-O ARM64, I'm questioning whether we need to expose this option to users explicitly in the way shown in the patch I referenced. 
My plan is to port the icf=safe_thunks optimization from Mach-O to ELF format and evaluate the potential binary size improvements. Currently, we use icf=safe with -faddrsig for some of our production ELF builds.

https://github.com/llvm/llvm-project/pull/106573