busybox's shells have no `--version`, and start an interactive shell instead,
so with `$SHELL` set to busybox `sh` on a terminal, `nvm debug` waited for input forever,
which hung the alpine `sh` CI lanes in the "mirror URL credentials are masked in output" test.
Like the other busybox tools, its version now comes from `--help`,
and every shell is given no stdin to read.