Add a flag in the debian/rules to stop rewriting shebang lines

[radujipa]

It seems like without this magic flag combined with --with python2 debuild thinks it's a grand idea to remove my shebang by default. 👎

It turns out to be the reason why this splash PR failed after a build...

I'm going to find me one of these deb devs one day 😈

[radujipa]

(1) As a user, I want a loading animation when I launch Settings app

[wizofe]

By the way I know one of those. I can introduce you to him 🤗