[llvm] [CI] Disable flang from pre-commit tests when Flang files are not touched (PR #93485)

[Renato Golin via llvm-commits]

rengolin wrote:

> > Isn't is tested in post-commit bots?
> 
> Yes, I just don't see the problem to have it in linux pre-commit since it was reliable so far until now. If it's a problem of build time or load then it's a different issue.

If there's a way to run on Linux but not Windows, then I don't mind. I just want to make sure we only add to pre-commit what we know is stable, but letting it run post-commit for a few months without .

https://github.com/llvm/llvm-project/pull/93485