Use /usr/bin/env in shebangs

This is guaranteed to work everything including NixOS

bin/kernel-hardening-checker

-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 # For using the tool without installation via setuptools
 

kernel_hardening_checker/__init__.py

-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 """
 This tool is for checking the security hardening options of the Linux kernel.

kernel_hardening_checker/checks.py

-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 """
 This tool is for checking the security hardening options of the Linux kernel.

kernel_hardening_checker/engine.py

-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 """
 This tool is for checking the security hardening options of the Linux kernel.

kernel_hardening_checker/test_engine.py

-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 """
 This tool is for checking the security hardening options of the Linux kernel.

setup.py

-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 from setuptools import setup