What is the function to terminate to the OS with a given exit code?

As background I am using CMU Lisp to write a language front end to GCC.

I have spent about an hour looking in the docs for this function to no
avail. Peraps I should use the FFI?

In C it is (exit n)

In gcl it is (by n)
In SBCL it is (sb-ext:quit n)
In CLISP (EXT:EXIT &OPTIONAL status)
In CMU...

Also how should I have been able to find this?

Thanks,
Tim Josling