[llvm] [lit] Echo full RUN lines in case of external shells (PR #66408)

[via llvm-commits]

dyung wrote:

> Fixed another instance of that: [30d77fb](https://github.com/llvm/llvm-project/commit/30d77fb80857e645b300c8f59cad9414d090e083)

Thanks for the quick fix, was just about to comment on that! Hopefully that's the last of them!

https://github.com/llvm/llvm-project/pull/66408