[Toybox] Extra echo in mkroot for passwd

[Denys Nykula]

Hi, 24ae822 scripts/mkroot.sh writes a bad passwd so my nightly couldn't su:

 cat > "$ROOT"/etc/passwd << 'EOF' &&
-root::0:0:root:/root:/bin/sh
+echo -e 'root::0:0:root:/root:/bin/sh

> ...
> su: user 'root': Bad file descriptor

What change did you intend in this bit? Also the output started having this line
I don't remember from before when building without LINUX env set:

> === create x86_64-linux-musl-root.cpio.gz