Redo the jq presence test

dist/steps/run_tests.sh

@@ -43,6 +43,12 @@ echo "Using Unity version \"$UNITY_VERSION\" to test."
 if [ "$PACKAGE_MODE" = "true" ]; then
   echo "Running tests on a Unity package rather than a Unity project."
 
+  if ! command -v jq &> /dev/null
+  then
+      echo "jq could not be found. This is required for package mode, and is likely the result of using a custom Docker image. Please use the default image or install jq to your custom image."
+      exit 1
+  fi
+
   echo ""
   echo "###########################"
   echo "#    Package Folder       #"