When set to `true`, this added `wipe` property will completely remove the target directory contents (except hidden files) before copying the build files into it.
The instruction is only allowed if `directory` is **not** `/` as a tiny and very inadequate measure against unintentional destruction of the host system.
Rather than using `xargs` which behaves differently on BSD and Linux, it's safer to use the straight `cp`. We lose the output of which files were copied - but I'd be more than happy to add this as a separate command to list which files were copied and which were ignored.
