[llvm] [llvm-strip] Remove empty SHT_GROUP sections. (PR #97141)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> Currently llvm-strip in --strip-debug mode doesn't remove such sections. 

Thanks for noticing this. This applies to other section removal operations like --remove-section, so another test will be useful

https://github.com/llvm/llvm-project/pull/97141