The stock build instructions make a lot of assumptions on the status (presence and configuration) of some extra dependencies. (Original instructions from: https://github.com/alacritty/alacritty/blob/master/INSTALL.md )
Here is something more coherent:
Run (Yes to install/proceed):
sudo apt install git curl cargo cmake pkg-config libfreetype6-dev libfontconfig1-dev libxcb-xfixes0-dev libxkbcommon-dev python3