'U' is default and deprecated since python-3.3, becomes a failure in 3.11.

Just a quick fix (rather than bump waf) while waiting for upstream's
plans to migrate to meson:
https://github.com/jackaudio/jack2/issues/898
--- a/waflib/ConfigSet.py
+++ b/waflib/ConfigSet.py
@@ -314,3 +314,3 @@
 		tbl = self.table
-		code = Utils.readf(filename, m='rU')
+		code = Utils.readf(filename, m='r')
 		for m in re_imp.finditer(code):
--- a/waflib/Context.py
+++ b/waflib/Context.py
@@ -664,3 +664,3 @@
 	try:
-		code = Utils.readf(path, m='rU', encoding=encoding)
+		code = Utils.readf(path, m='r', encoding=encoding)
 	except EnvironmentError: