sdk build: don't upload empty jars to maven from sdk project

sdk/build.gradle

@@ -418,7 +418,7 @@ task cleanSdk() <<{
     file("JME3TestsTemplateAndroid/src/jmetest/").deleteDir()
 }
 
-jar.dependsOn(buildSdk)
-clean.dependsOn(cleanSdk);
-
+tasks.remove(uploadArchives)
 
+jar.dependsOn(buildSdk)
+clean.dependsOn(cleanSdk)