message: guix-verify: Non-zero exit code when anything fails
  Previously, if verification fails, the correct message will be printed,
  but the exit code would still be 0.
diff: @@ -77,11 +77,13 @@ verify() {
  echo ""
  echo "Hint: Either the signature is invalid or the public key is missing"
  echo ""
  + failure=1
  elif ! diff --report-identical "$compare_manifest" "$current_manifest" 1>&2; then
  echo "ERR: The SHA256SUMS attestation in these two directories differ:"
  echo " '${compare_manifest}'"
  echo " '${current_manifest}'"
  echo ""
  + failure=1
  else
  echo "Verified: '${current_manifest}'"
  echo ""
  @@ -166,3 +168,7 @@ if (( ${#all_noncodesigned[@]} + ${#all_all[@]} == 0 )); then
  echo ""
  exit 1
  fi
  +
  +if [ -n "$failure" ]; then
  + exit 1
  +fi
  