[clang] [flang] [flang][draft] Improve debug info generation. (PR #84202)

[via cfe-commits]

abidh wrote:

Thanks @kiranchandramohan and @tblah for your comments. I do plan to work on this long term to bring the full debug support to flang. I will work on creating a design document.

https://github.com/llvm/llvm-project/pull/84202