infrastructure: Use CMake instead of the current build system

[cristian-vijelie]

The current build system, with included Makefiles from 6 folders up in the directory tree seems to me like reinventing the wheel. We should consider using a more standardised build system, like CMake, ninja or the like

[teodutu]

We have this in mind somehow. I introduced the generic makefiles in #6 because I was always copying and pasting the same makefile to every exercise. But now this makes extracting a single exercise (if you want to use it in another context such as another class) difficult. Using CMake seems to be a solution for most of our troubles.

[gabrielmocanu]

Bazel might be a solution. We need someone to take ownership on this.😁