Add fatJar rule to build.gradle.

Author: yichen0831

build.gradle

@@ -37,3 +37,12 @@ dependencies {
     // Use JUnit test framework
     testImplementation 'junit:junit:4.12'
 }
+
+task fatJar(type: Jar) {
+    from {
+        configurations.runtimeClasspath.collect {
+            it.isDirectory() ? it : zipTree(it)
+        }
+    }
+    with jar
+}