Only /bin/sh is needed for img2fwup
-#!/bin/bash
+#!/bin/sh
set -e
IMGFILE=$1
FWFILE=$2
-if [[ -z "$IMGFILE" ]]; then
+if [ -z "$IMGFILE" ]; then
echo "Compress an image file into a .fw archive so that it can be written to a"
echo "MicroSD card using fwup."
echo
