Add r8-sources.jar to output

Bug: b/270105162
Change-Id: Id6b9ff75179259a1a504112b7f9a7cebe518e357
diff --git a/d8_r8/keepanno/build.gradle.kts b/d8_r8/keepanno/build.gradle.kts
index 97cd877..56d1ea0 100644
--- a/d8_r8/keepanno/build.gradle.kts
+++ b/d8_r8/keepanno/build.gradle.kts
@@ -13,6 +13,7 @@
   }
   sourceCompatibility = JvmCompatibility.sourceCompatibility
   targetCompatibility = JvmCompatibility.targetCompatibility
+  withSourcesJar()
 }
 
 dependencies {