Only include annotation parts in keepanno-annotations.jar

Bug: 301573288
Change-Id: I0bb45a8b8a50eec247af24c0f1d7530027088902
diff --git a/d8_r8/keepanno/build.gradle.kts b/d8_r8/keepanno/build.gradle.kts
index 56d1ea0..9d4a18e 100644
--- a/d8_r8/keepanno/build.gradle.kts
+++ b/d8_r8/keepanno/build.gradle.kts
@@ -10,6 +10,7 @@
 java {
   sourceSets.main.configure {
     java.srcDir(getRoot().resolveAll("src", "keepanno", "java"))
+    java.include("com/android/tools/r8/keepanno/annotations/*.java")
   }
   sourceCompatibility = JvmCompatibility.sourceCompatibility
   targetCompatibility = JvmCompatibility.targetCompatibility