[clang] [flang] [Flang][Driver] Add -print-resource-dir command line flag to emit Flang's resource directory (PR #90886)

[Michael Klemm via cfe-commits]

mjklemm wrote:

> Do you know the meaning for Classic Flang?

The way `-print-resource-dir` now works should be consistent with how Classic Flang works.  If that's not the right response, I guess I got my wires crossed and you need to explain it to me. :-) 

https://github.com/llvm/llvm-project/pull/90886