After struggling with this problem for a few hours, I found the solution. The avr package it downloads, or tries to download results in a corrupt archive file avr-gcc-7.3.0-atmel3.6.1-arduino7-i686-w64-mingw32.zip
In a browser go to this URL: https://downloads.arduino.cc/tools/avr-gcc-7.3.0-atmel3.6.1-arduino7-i686-w64-mingw32.zip
Save or move the file here (overwrite the corrupt one that is there):
C:\Users\username\AppData\Local\Arduino15\staging\packages (substitute your username for username)
- If you can't see the AppData folder while in File Explorer, Select the "View" tab and, make sure "Hidden Items" is checked.
Start the Arduino IDE and it should install automatically with no errors in the CLI. If you go to Tools -> Boards -> Boards Manager, you should see avr 1.8.6 installed.
I hope this helps someone that is running into this same problem.
Cheers.
- Edit 10/24/2023 added instructions for turning on hidden items.