contrib/jenkins.sh: run "make maintainer-clean"

Related: OS#3047
Change-Id: I20997b986b24ced9bb8d6d66a66d5ec2bafd00f2
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index ebdc6ea..43e81a1 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -8,5 +8,6 @@
 ./configure --enable-sanitize CFLAGS="-Werror" CPPFLAGS="-Werror"
 $MAKE $PARALLEL_MAKE
 $MAKE distcheck
+$MAKE maintainer-clean
 
 osmo-clean-workspace.sh