Exclude empty directories in swiss army knife

These ends up in j8.jar breaking com.android.tools.r8.bootstrap.SanityCheck

Change-Id: I7ed95531f3214d089d586a361a9e7985fe2a3fdf
diff --git a/d8_r8/main/build.gradle.kts b/d8_r8/main/build.gradle.kts
index 8cab192..989b99a 100644
--- a/d8_r8/main/build.gradle.kts
+++ b/d8_r8/main/build.gradle.kts
@@ -283,6 +283,8 @@
     dependsOn(swissArmyKnife)
     from(swissArmyKnife.get().outputs.files.map(::zipTree))
     exclude("LICENSE")
+    exclude("androidx/")
+    exclude("androidx/annotation/")
     exclude("androidx/annotation/keep/**")
     archiveFileName.set("swiss-army-no-license.jar")
 }