[clang] [flang] [flang][Driver] Support -gsplit-dwarf. (PR #160540)

[Abid Qadeer via cfe-commits]

================
@@ -131,20 +135,57 @@ void Flang::addOtherOptions(const ArgList &Args, ArgStringList &CmdArgs) const {
                    options::OPT_finstrument_functions});
 
   llvm::codegenoptions::DebugInfoKind DebugInfoKind;
+  bool hasDwarfNArg = getDwarfNArg(Args) != nullptr;
----------------
abidh wrote:

Yes, I added those for readability but have no strong opinion.

https://github.com/llvm/llvm-project/pull/160540