There is no makefile

[gilles-peskine-arm]

This project currently only supports CMake as a build system. That's fine when it's used in a project that itself only supports CMake as a build system, such as TF-M. But it complicates the life of other users (CMake is not easy to use or to integrate into other build systems, and chokes if the source directory contains spaces), and it complicates the life of maintainers (because CMake is inflexible and slow, which makes it poorly suited to everyday development).

The goal of this issue is to provide a build system based on make, which is standard, fast, flexible and easy to use.