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

[via llvm-commits]

dyung wrote:

> > There seems to be a race condition of sorts which has caused the test shtest-run-at-line.py to be a bit unreliable on a Windows bot: https://lab.llvm.org/buildbot/#/builders/216
> 
> Thanks for pointing that out. (And thanks for enabling FileCheck verbosity on this bot!)

Thanks for telling me how to, it is much more useful now!

> > ```
> >          8: bash.exe: warning: could not find /tmp, please create! 
> > ```
> 
> Do you know why this is being printed at all? Is it reasonable to just create that directory on that bot?

I could, although I vaguely recall having similar problems in the past trying to get rid of this error, but I can try. I would prefer that the test can handle it just in case though.

> > Can the test be restructured such that it can handle this?
> 
> I'm concerned about weakening the test and missing other problems. I might use `grep -v` to throw away that line. Is that portable to windows?

I'm not sure. I think there are some tests that still do use grep, but I think the usage of it is highly discouraged these days.

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