build-rootfs: Run ldconfig

Need to update the loader search path in the final root filesystem.

build-rootfs.sh

@@ -76,6 +76,8 @@ if [ -f /mnt/gentoo/etc/udev/hwdb.bin ]; then
     mv /mnt/gentoo/etc/udev/hwdb.bin /mnt/gentoo/usr/lib/udev/
 fi
 
+ldconfig -r /mnt/gentoo
+
 rm -f /mnt/gentoo/lib/tmpfiles.d/provision.conf
 systemd-tmpfiles --root=/mnt/gentoo -E --exclude-prefix=/var --create