TBR v23proxy: make clean more files

Change-Id: Ife854cc90f9d6aa1a94908895b29a7515789ddc5
diff --git a/Makefile b/Makefile
index 2504d10..205913e 100644
--- a/Makefile
+++ b/Makefile
@@ -245,9 +245,11 @@
 .PHONY: clean-go
 clean-go:
 	rm -rf gen
+	rm -rf mojom/mojo
 
 .PHONY: clean-dart
 clean-dart:
 	rm -rf lib/gen
 	rm -rf dart-examples/echo/lib/gen
 	rm -rf dart-examples/fortune/lib/gen
+	rm -rf packages