Fixing bug where build fails when there is no dist folder

Change-Id: I1e636543619ed9a9cc1d5b505376f23643f82a32
diff --git a/Makefile b/Makefile
index 5b6461f..b9083d5 100644
--- a/Makefile
+++ b/Makefile
@@ -69,7 +69,7 @@
     $<
 
 python-build: setup.py python-protos
-	rm -r dist/
+	rm -rf dist/
 	python ./setup.py sdist
 
 python-test: tox.ini setup.py python-protos