[llvm] [llvm-lit][test][NFC] Moved cat command tests into separate lit test file (PR #102366)

[Paul Kirth via llvm-commits]

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@@ -0,0 +1,20 @@
+## Check the cat command.
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ilovepi wrote:

Probably. It's likely to catch out tests that are added, but didn't update this file correctly. I'd expect it would be possible to miss them otherwise.

https://github.com/llvm/llvm-project/pull/102366