Add empty xxx-javadoc.jar for Maven Central

Author: elizarov

gradle/publish-bintray.gradle

@@ -38,6 +38,12 @@ task sourcesJar(type: Jar) {
     from "src/main/kotlin"
 }
 
+// empty xxx-javadoc.jar
+task javadocJar(type: Jar) {
+    classifier = 'javadoc'
+    from "$buildDir/javadoc" // would not exist
+}
+
 if (!project.name.endsWith("-native")) {
     publishing {
         repositories {
@@ -47,6 +53,7 @@ if (!project.name.endsWith("-native")) {
             maven(MavenPublication) {
                 from components.java
                 artifact sourcesJar
+                artifact javadocJar
                 if (project.name.endsWith("-maven-plugin")) {
                     pom.with {
                         packaging = 'maven-plugin'