Runit services should be long running services, but oneshot services exist, so the pause executable is used to implement oneshot functionality in runit. You need to compile pause.c because
it isn't worth making a package for it as it's source code is so short. The produced executable should be in discoverable from your $PATH, preferably in /usr/local/bin as it's compiled. You can use any C compiler
To test that it succeeded, type pause and hit Enter. It should "pause" the terminal you were running. To stop, do Ctrl-C as that will send a kill signal to the process.