Do not symlink /usr/local/{bin,sbin,lib}, instead add them to PATH in /init
The symlinks cause issues since after switch root, the resolved paths to binaries suddenly are not valid anymore.
To still support launching executables from /usr/local/sbin and /usr/local/bin without calling them by their full path, add them to PATH.
Since it does not appear to be possible to build busybox with a custom default PATH, export it in /init instead.