Please see the project documentation in Read the docs.
Zephyr based RTOS multiapp framework
Source the tsip-env.sh to get appropriate environment variables for the project. It will source the zephyr-env.sh as well.
The tsip-env.sh takes the application name and the board as parameters. The application name is used to compile the app using src/main-<app_name>.c source file.
E.g.:
$ . tsip-env.sh test native_posix