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

[Paul Kirth via llvm-commits]

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@@ -0,0 +1,33 @@
+## Tests to check cat -e output for ASCII characters and newlines
+
+# RUN: cat -e %S/txt-files/allchars | FileCheck %s --check-prefix=ALLCHARS
+# RUN: cat -e %S/txt-files/newline | FileCheck %s --check-prefix=NEWLINE
+
+# ALLCHARS: ^@^A^B^C^D^E^F^G^H      $
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ilovepi wrote:

```suggestion
# ALLCHARS: ^@^A^B^C^D^E^F^G^H
# ALLCHARS-SAME: $
```
May want to exclude chars that we can't output/see in the FileCheck line.`{{.*}}$` could also work.

My concern is those just look like whitespace, but are probably something else.

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