Executables than can be called with `exec()` live in here.
Symlinks work.

Unfortunately, only wizards can use `exec`, but it's possible to wrap exec in another verb.

```
> ;exec({"cat", "/etc/os-release"})
=> {0, "PRETTY_NAME=\"Debian GNU/Linux 13 (trixie)\"~0ANAME=\"Debian GNU/Linux\"~0AVERSION_ID=\"13\"~0AVERSION=\"13 (trixie)\"~0AVERSION_CODENAME=trixie~0ADEBIAN_VERSION_FULL=13.0~0AID=debian~0AHOME_URL=\"https://www.debian.org/\"~0ASUPPORT_URL=\"https://www.debian.org/support\"~0ABUG_REPORT_URL=\"https://bugs.debian.org/\"~0A", ""}
```