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

[Konrad Kleine via cfe-commits]

kwk wrote:

> I believe it's important to add a test. Similar to `clang/test/Driver/gcc-triple.cpp`.

@tuliom, thank you for pointing this out. I've added tests now.



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