[flang-commits] [flang] [flang][debug] Add support for common blocks. (PR #112398)

[Abid Qadeer via flang-commits]

abidh wrote:

> > @jeanPerier Would you mind letting @abidh 's PR in and then he will make adjustment based on FIR extensions later.
> 
> Yes, you can go ahead and update/merge this and I will ping you when I have the FIR changes.

I have rebased the PR. I made a small change to address the comments that `DW_AT_external` should true for these variables in `DWARF` as it is in other compilers. Please let me know if you have any further comments.

https://github.com/llvm/llvm-project/pull/112398