[flang-commits] [flang] [NFC] Adding missing flang tests for LTO bugfix (PR #80417)

[Paschalis Mpeis via flang-commits]

paschalis-mpeis wrote:

Thanks Tom.

For the rest of the reviewers, the tests added are mirroring [these clang tests](https://github.com/llvm/llvm-project/pull/78749/files#diff-ee7e6c27dc24f2fd427618b91a1f1a997f6067089623013f81a1a9d84688de5e)
- from #78749

https://github.com/llvm/llvm-project/pull/80417