Ensure to invoke the Busybox `passwd` applet to change the system password
in a non-interactive manner. Non-Busybox variants may not take the new
password input from stdin or use password hashes which are not supported
by musl's `crypt()` implementation by default.
Fixes: #5629
Signed-off-by: Jo-Philipp Wich <jo@mein.io>
(cherry picked from commit 22e2bfb09667e167a93b5eca4487ac41669126d9)
4ec18ec765