[lld] [lld][MachO] Fix symbol insertion in `transplantSymbolsAtOffset` (PR #120737)

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alx32 wrote:

About adding a test for this - `lld/test/MachO/alias-symbols.s` triggers the insert. Currently all the offsets are 0's so the position doesn't matter.
I think we should be able to slightly tweak `alias-symbols.s` to insert a symbol with a non-zero offset and then add an `assert(std::is_sorted)` at the end of `transplantSymbolsAtOffset` and that will be our test. Have you looked into weather this is possible ? 

https://github.com/llvm/llvm-project/pull/120737