update clean spec

Change-Id: Ia511131fb55916690a3d459c7ab1e7b7ddb26c4b
diff --git a/CleanSpec.mk b/CleanSpec.mk
index 08503b4..e5f1f90 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -80,6 +80,7 @@
 $(call add-clean-step, rm -rf $(OUT_DIR)/target/common/obj/JAVA_LIBRARIES/framework_intermediates/src/core/java/android/content/IClipboard.P)
 $(call add-clean-step, rm -rf $(OUT_DIR)/target/common/obj/JAVA_LIBRARIES/framework_intermediates/src/telephony/java/com/android/internal/telephony/ITelephonyRegistry.P)
 $(call add-clean-step, rm -rf $(OUT_DIR)/target/common/obj/JAVA_LIBRARIES/android_stubs_current_intermediates)
+$(call add-clean-step, rm -rf out/target/common/docs/api-stubs*)
 
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST