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

[Paul Kirth via llvm-commits]

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@@ -0,0 +1,19 @@
+# RUN: cat -e %S/txt-files/allchars | FileCheck %s
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ilovepi wrote:

A comment at the top of the file describing the purpose of this test would be welcome, especially since its not obvious what all the special character matching is for/doing.

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