What does it mean - writing a minivan?

Please see the img below.

What does "write me a new minivan" mean here?

PS: I am from a non English Speaking country.

Wally, the engineer who is going "write a mini-van", is going to intentionally abuse the incentive system by intentionally creating bugs, then claiming the ten-dollar bonus for fixing each bug. That can be done much faster than finding and fixing existing bugs, so it's a quick way to "earn" enough money to buy a minivan.

The larger point of the comic is that misaligned incentives create bad behavior, and that the people who create misaligned incentives don't realize when they do so:

• The boss wonders about whether it will "drive the right behavior", but doesn't have enough wisdom to realize that it won't.
• The engineers (portrayed as being smarter than their boss) immediately see how to exploit the terrible incentive program, and celebrate.