Add jarRelease task

library/build.gradle

@@ -36,3 +36,14 @@ android {
 
 dependencies {
 }
+
+android.libraryVariants.all { variant ->
+    def name = variant.buildType.name
+    if (name.equals(com.android.builder.core.BuilderConstants.DEBUG)) {
+        return; // Skip debug builds.
+    }
+    def task = project.tasks.create "jar${name.capitalize()}", Jar
+    task.dependsOn variant.javaCompile
+    task.from variant.javaCompile.destinationDir
+    artifacts.add('archives', task);
+}