Python 3.12 warns on invalid escape sequences
https://github.com/python/cpython/pull/99011
https://github.com/libfirm/libfirm/pull/34

Index: scripts/filters.py
--- scripts/filters.py.orig
+++ scripts/filters.py
@@ -6,7 +6,7 @@ import re
 
 
 def filtjoin(string, joinstring):
-    args = re.split('\s*\n\s*', string)
+    args = re.split(r"\s*\n\s*", string)
     if args[0] == '':
         args = args[1:]
     if len(args) > 0 and args[-1] == '':
