This project is in its extremely early days. Don't expect anything too interesting here
You should have a cross-compiler for the architecture you wish to build for. A good guide on how to do this can be found on the OS Dev wiki. At the moment, the build system assumes it to be a fork of GCC, and thus looks for (ARCH)-gcc in your path.
If you are using CLion (or any other IDEA IDE), you should go to Build, Execution, and Deployment -> Toolchains, create one for this project, and select your cross-compiler for your target architecture. This will stop CLion from always assuming a hosted environment.