test: add a test to confirm scala/scala#10644 is forward-ported

compiler/test/dotc/run-test-pickling.blacklist

@@ -44,3 +44,5 @@ t6138
 t6138-2
 i12656.scala
 trait-static-forwarder
+i17255
+

tests/run/i17255/J.java

@@ -0,0 +1,13 @@
+package p;
+
+public class J {
+	public static J j = new J();
+	public static p.J f() {
+		return p.J.j;
+	}
+	public static p.Module$ module() {
+		return p.Module$.MODULE$;
+	}
+
+	public String toString() { return "J"; }
+}

tests/run/i17255/Module.scala

@@ -0,0 +1,10 @@
+package p {
+  object Module {
+    override def toString = "Module"
+  }
+}
+
+object Test extends App {
+  assert(p.J.f().toString == "J")
+  assert(p.J.module().toString == "Module")
+}