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

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> > 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.

I guess it depends on which testsuite it is. The main llvm testsuite (and the other ones that use the same base setup) rely on a handful of unix-like tools, and will implicitly try to find them from an installation of Git for Windows, unless otherwise available: https://github.com/llvm/llvm-project/blob/llvmorg-17.0.1/llvm/utils/lit/lit/llvm/config.py#L29-L34

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