Configuration-free build system for C++17

This is my first stab at a configuration-free build system for C++17. Tested on macOS, Arch Linux and Ubuntu 17.10. The idea is to make something that is as easy as go build for building executables.

It takes a lot of hassle away from building or starting small C++17 projects, and it auto-detects libraries.

It uses `pkg-config` and pacman/apt/homebrew for finding compilation flags only based on included headers. Examples for configuration-free use of GTK+3 and SDL2 are included in the project.

Of course, some projects need additional configuration, but the idea is that compliant projects may advertise themselves as "configuration free".

Feedback is welcome.