Makefile: Fix race condition in submodule initialization

6 jobs for python3-test in 2 minutes and 13 seconds
Status Job ID Name Coverage
  Test
passed #3956
docker linux amd64
test:python2:comparative:kresd

00:01:34

passed #3954
docker linux amd64
test:python2:pep8

00:01:55

passed #3955
docker linux amd64
test:python2:pylint

00:01:35

passed #3959
docker linux amd64
test:python3:comparative:kresd

00:02:12

passed #3957
docker linux amd64
test:python3:pep8

00:00:31

passed #3958
docker linux amd64
test:python3:pylint

00:01:43