[clang] SyntaxWarning: invalid escape sequence '\s' with Python3.12

llvm-project/clang/tools/libclang/linker-script-to-export-list.py:9: SyntaxWarning: invalid escape sequence '\s'
  m = re.search("^\s+(clang_[^;]+)", line)

Cherry-picked from 7851670

Author: adriweb

clang/tools/libclang/linker-script-to-export-list.py

@@ -6,6 +6,6 @@
 output_file = open(sys.argv[2], 'w')
 
 for line in input_file:
-    m = re.search('^\s+(clang_[^;]+)', line)
+    m = re.search(r'^\s+(clang_[^;]+)', line)
     if m:
         output_file.write(m.group(1) + "\n")