[llvm] [LLVM] Do not require shell for some tests (PR #94595)

[Jay Foad via llvm-commits]

jayfoad wrote:

> Yeah I think `ln` qualifies as deserving a `REQUIRES: shell` ?

I don't think so. `REQUIRES: shell` means the RUN lines need to be run using bash instead of lit's internal shell, but (as @petrhosek said) the internal shell can still run external commands like /usr/bin/ln.

I think `UNSUPPORTED: system-windows` is probably more appropriate on the grounds that Windows doesn't have Unix-like symlinks.

> For the unicode thing, seems sketchy to expect it to work on Windows. I cut the file down to just the `echo` command and tried to run it on my box, and got junk out.

This sounds similar to the printf problems that were worked around in #83907, and again the solution was `UNSUPPORTED: system-windows`.

https://github.com/llvm/llvm-project/pull/94595