You can build aerOS successfully if you get archiso.
This is a package supplied by Arch Linux that will allow you to build aerOS.
You can check the package version here.
We are working to ensure that aerOS can be always built with the latest version of archiso.
If it doesn't, please open an issue, and we will fix it.
Run sudo pacman -Q archiso before running the build script, then you can proceed to building.
To build aerOS, run time ./build.sh and wait. After some time you should receive your copy of aerOS. Enjoy!