contrib/jenkins: Enable parallel make in make distcheck

Change-Id: Ife6c5b37ce34923a3379703bc6460a5760a815e8
Related: OS#4421
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index c23bdec..20314e5 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -15,8 +15,8 @@
 autoreconf --install --force
 ./configure --enable-werror
 $MAKE $PARALLEL_MAKE
-$MAKE distcheck \
+$MAKE $PARALLEL_MAKE distcheck \
   || cat-testlogs.sh
-$MAKE maintainer-clean
+$MAKE $PARALLEL_MAKE maintainer-clean
 
 osmo-clean-workspace.sh