Fair warning, I'm about to remove glew from the repository and from now on it will be obtained via your package manager like the rest of ENIGMA's dependencies.https://github.com/enigma-dev/enigma-dev/pull/1226
Josh felt it appropriate to warn everybody, and I agree. If you update to master now you will need to have glew installed:
sudo apt-get install libglew-dev
pacman -Sy glew
pacman -Sy mingw-w64-x86_64-glew
brew install glew
This is important because ENIGMA should not distribute its dependencies this way. For one, they are not our code and distort the code coverage, and second they end up getting really old and crufty (like the current glew) which also leads to security vulnerabilities.