I thought the software was some kind of bizarre esoteric thing but it's literally just cmake.
Install an ARM toolchain and then run cmake. Have to run in the MinSizeRel config:
cmake -DCMAKE_BUILD_TYPE=MinSizeRel
cmake --build . --config MinSizeRel
This is actually pretty clean C++. Not sure why it'd take much to port it.
VS Code has full cmake integration with its C++ tools. About as good as you can get and way better than most garbage vendor tooling.