[clang] [Driver] Link Flang runtime on Solaris (PR #65644)

[Andrzej Warzyński via cfe-commits]

banach-space wrote:

> I wonder how to proceed with the patch at hand.

I'm not a Solaris expert, but based on this discussion I'd consider adding support for `-fuse-ld` in Flang. This sort of changes are often as simple as updating Options.td. Same for `-r`.

One important rule of thumb that I'd stick to:
* Do whatever Clang, GFortran and GCC do.

In cases where there's different behavior between these compilers, just go for whatever feels most sensible, but please document your design decision.

https://github.com/llvm/llvm-project/pull/65644