RFE: Add --list to multi-call binary (like busybox/uutils)

```
$ busybox
BusyBox v1.36.1 () multi-call binary.
BusyBox is copyrighted by many authors between 1998-2015.
Licensed under GPLv2. See source distribution for detailed
copyright notices.

Usage: busybox [function [arguments]...]
...
Currently defined functions:
# returns exit code 0

$  gnu58d88d243/coreutils
Try gnu58d88d243/coreutils --help' for more information.
# returns 1
```