[clang] [flang] [llvm] [openmp] [flang][driver] rename flang-new to flang (PR #110023)

[Brad Richardson via cfe-commits]

everythingfunctional wrote:

> @everythingfunctional with this change and install, we are installing flang with the -20 in the install dir: `-- Installing: /build/source/debian/tmp/usr/lib/llvm-20/bin/flang-20`
> 
> it should not be the case, it should be named `/usr/lib/llvm-20/bin/flang` to match what is done elsewhere

Forgive me if I misunderstood or implemented this incorrectly, but I was under the impression (based on [an earlier comment](https://github.com/llvm/llvm-project/pull/110023#issuecomment-2378556647)) that this was the intended behavior.

https://github.com/llvm/llvm-project/pull/110023