[clang] [flang][driver] support -dumpversion and -dumpmachine (PR #68896)

[Andrzej Warzyński via cfe-commits]

banach-space wrote:

> > Could this be implemented without any updates to Clang (beyond Options.td)?
> 
> The options could work by changing options.td only. However, `CLANG_VERSION_STRING` and `FLANG_VERSION_STRING` could be different. This is to handle that.

You are adding a support for these new flags in `flang-new`, which is implemented in terms of `clangDriver` - this scenario would be very unlikely at the moment. And even if that was desired, you'd need to update Flang's driver too. I'd rather keep this to the required minimum. If you really want to keep this, you will need to update flang/tools/flang-driver/driver.cpp too.

https://github.com/llvm/llvm-project/pull/68896