[llvm] [llvm-lit][test] Precommit tests for lit's built-in cat command (PR #101530)

[via llvm-commits]

================
@@ -0,0 +1,31 @@
+## Test the cat command
+
+# RUN: not %{lit} -a -v %{inputs}/shtest-cat \
+# RUN: | FileCheck -match-full-lines %s --dump-input-context=1000
----------------
connieyzhu wrote:

Oh, that was just to get more context as I was debugging. I can remove that in my next patch

https://github.com/llvm/llvm-project/pull/101530