[llvm] [llvm-objcopy] Remove references for empty section groups (PR #98106)

[Fangrui Song via llvm-commits]

MaskRay wrote:

Since https://github.com/llvm/llvm-project/pull/97141 has been reverted, this now needs a rebase and restoring the original test file:)

https://github.com/llvm/llvm-project/pull/98106