[llvm] fix(llvm/**.py): fix invalid escape sequences (PR #94035)

[Nikita Popov via llvm-commits]

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@@ -17,24 +17,24 @@ def remove_prefix(i, d=0):
             p = r.group(1)
             s = re.sub("=" + p + ",", "=", s)
             s = re.sub("," + p + "([, \n])", "\\1", s)
-            s = re.sub("\s+-?-check-prefix=" + p + "([ \n])", "\\1", s)
+            s = re.sub("\\s+-?-check-prefix=" + p + "([ \n])", "\\1", s)
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nikic wrote:

```suggestion
            s = re.sub(r"\s+-?-check-prefix=" + p + "([ \n])", "\\1", s)
```

https://github.com/llvm/llvm-project/pull/94035