fix: used sha256 to generate the checksum for the rootfs.img

Signed-off-by: yash-zededa <yash@zededa.com>

.github/workflows/assets.yml

@@ -110,7 +110,7 @@ jobs:
           for asset in assets/*; do
             mv "$asset" "assets/${{ env.ARCH }}.$(basename "$asset")"
           done
-          md5sum "assets/${{env.ARCH}}.rootfs.img" > assets/"${{env.ARCH}}.rootfs.img.md5"
+          sha256sum "assets/${{ env.ARCH }}.rootfs.img" | awk '{ print $1 }' > "assets/${{ env.ARCH }}.rootfs.img.sha256"
       - name: Upload binary to GitHub Release
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}