[llvm] [lit] Are all RUN lines skipped in windows cmd? (PR #65242)

[Joel E. Denny via llvm-commits]

jdenny-ornl wrote:

> I have no stake in Apple/Swift, but for myself, `cmd` is the natural shell to use on Windows. (When I install Visual Studio, it creates a widget that brings up a `cmd` shell with the right environment. I'm not aware of a similar widget for PowerShell.) While I rarely try to copy-paste from a `lit` dump into `cmd` (the commands are generally too full of long paths to temp locations to work well) I think it would be good (but not mandatory) for that copy-paste to actually work.
> 
> Like others have said, I had not really grokked that Windows defaults to the internal shell, although just this week I tripped over a behavioral difference in how `diff` works in the two environments (not related to your patches). So, if there seems to be benefit to making the external shell Just Not Work on Windows, I wouldn't lose a lot of sleep over it.

In case it isn't clear, there are two somewhat orthogonal issues here:

- This PR is about whether lit can execute RUN lines in `cmd`.  That does not appear to have worked since April, 2022. 
- The copy-paste issue is about whether lit can print RUN lines in a form that the user can easily copy to `cmd`.  For RUN lines that were written for lit's internal shell, that might require lit to *translate* the RUN lines to a form compatible with `cmd`.  I say might because I don't have much experience there.  The `diff` example above sounds like an example.



https://github.com/llvm/llvm-project/pull/65242