Windows OS build triggers antivirus: Trojan:Win32/Wacatac.B!ml

## Problem
Seeing a trojan warning after downloading the app is not a great way to introduce Flutter to a wider audience.

![image](https://user-images.githubusercontent.com/61761672/109863928-496e9800-7c73-11eb-8d75-027e0693f8de.png)

## Environment

**OS:** 64-bit Window 10 20H2 (build 19042.804)