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

[Thomas Preud'homme via llvm-commits]

RoboTux wrote:

> > LGTM.
> 
> Thanks for the quick review!
> 
> > Note: I've only looked at third commit as instructed, that is: [a398f3e](https://github.com/llvm/llvm-project/commit/a398f3e1dfbfc83489e4d85fd74e8b3f12d469e9)
> 
> You mean [d71c72c](https://github.com/llvm/llvm-project/commit/d71c72c9f20ed34dc2fe2d0ec849a6e44dbf9d20), right? [a398f3e](https://github.com/llvm/llvm-project/commit/a398f3e1dfbfc83489e4d85fd74e8b3f12d469e9) is the first commit.

Sadly not. I never remember if top is older or newer. Sorry, I'll review it now then. Please ignore my approval for now.

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