[clang] [flang] [flang][driver] Bring --gcc-triple to flang (PR #165886)

[Tarun Prabhu via cfe-commits]

tarunprabhu wrote:

> > Out of curiosity, did the absence of `--gcc-triple` cause any problems?
> 
> Yes, it caused a problem. In case of multiple gcc installations candidate, we couldn't select the right one by using a triple but instead had to specify the `--gcc-install-dir` which includes the gcc version information. In case the major gcc version changes we would have to rebuild llvm which isn't what we wanted.

Got it. 

> No I didn't. Is that required in this case? Want me to create one?

Not required at all. I was just wondering if I missed something that you might have filed. 

https://github.com/llvm/llvm-project/pull/165886