Fix the Gradle 6+ issue from #119.

Author: nedtwigg

build.gradle

@@ -37,6 +37,10 @@ subprojects {
 // local eclipse maven (created by Goomph)
 maven {
 url rootProject.file('target.p2/build/p2asmaven/maven')
+metadataSources {
+mavenPom()
+artifact()
+}
 }
 }
 }