example of known good gradle version

README.md

@@ -10,6 +10,13 @@ Install dependencies:
 
     sudo apt-get install gradle
 
+Your system may have a version of gradle that is too old. Gradle 5.6.1 is known
+to work well:
+
+    wget https://services.gradle.org/distributions/gradle-5.6.1-bin.zip
+    unzip gradle-5.6.1-bin.zip
+    export PATH=$HOME/gradle-5.6.1-bin:$PATH
+
 Clone and compile:
 
     git clone https://github.com/MyHush/SilentDragonWormhole