https://github.com/cmc-labo/tinyos-rtos/blob/2a47496047fdb45...
"Context switch (to be implemented in assembly for target architecture)"
There's no asm in the repo so I can only assume this is not something that actually compiles and runs.
Other things that are missing:
- No startup code (stack setup etc.)
- No linker script ("to be created", per makefile comment)