build: path improvements

Use correct paths in date.py

Fix some build warnings

build-aux/date.py

@@ -1,9 +1,15 @@
-#!/bin/env python
-#The MacOS 'date' is not quite up to GNU standards
+#!/usr/bin/env python3
+
+"""
+Script to get date strings, since the MacOS 'date' is not quite up to GNU
+standards
+
+E.g..
+  date.py 2023-10-14 "The year-month is %y %m"
+"""
+
 import sys
 from datetime import datetime
+
 date=datetime.strptime(sys.argv[1],'%Y-%m-%d')
 print(date.strftime(sys.argv[2]))
-#
-#  ./date.py 2023-10-14 "The year-month is %y %m"
-#