sys-apps/shadow: Ensure /bin is present before moving file into it

When building with a new prefix, sometimes the /bin directory
does not exist at install time. Therefore, we need to create it
before using it.

You can recreate if you try to run:
emerge --prefix=/test shadow

Closes: https://github.com/gentoo/gentoo/pull/10107
Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Signed-off-by: Mike Gilbert <floppym@gentoo.org>

sys-apps/shadow/shadow-4.6.ebuild

@@ -110,6 +110,7 @@ src_install() {
 	doins "${FILESDIR}"/default/useradd
 
 	# move passwd to / to help recover broke systems #64441
+	dodir /bin
 	mv "${ED%/}"/usr/bin/passwd "${ED%/}"/bin/ || die
 	dosym ../../bin/passwd /usr/bin/passwd