[llvm-lit] Resolve TypeError in built-in cat -v implementation (#98363)

Summary:
When using -v in lit's internal implementation of cat, there is a
TypeError when the file data is passed into convertToCaretAndMNotation()
as a str, because bytearray() requires an encoded string. This patch
encodes the str before passing it through bytearray().

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Differential Revision: https://phabricator.intern.facebook.com/D60250995

Author: connieyzhu

llvm/utils/lit/lit/builtin_commands/cat.py

@@ -10,7 +10,7 @@
 def convertToCaretAndMNotation(data):
     newdata = StringIO()
     if isinstance(data, str):
-        data = bytearray(data)
+        data = bytearray(data.encode())
 
     for intval in data:
         if intval == 9 or intval == 10: