Shutting off broiler pilot completely
You can just blow out the pilot light and once it cools down (a few minutes at worst), the pilot light assembly will shut off the gas. A pilot light for a stove has a safety device called a thermocouple that is tied to a valve as a safety precaution against accidentally losing the pilot flame. 

Relighting it will not be simple however. When you want to re-light it, you have to hold a reset button down while applying a flame to that device long enough to get it to open the valve again. That is not something for the faint of heart and is not something you want to do every time you want to use the oven...

Here's a video of the typical procedure (yours may vary slightly) if you want to assess your desire to go down this road.
https://www.youtube.com/watch?v=glX70JM-aFY