Makefile.inc1: attempt to fix pkgbase building

After b44147bb12450bdf851a519d1cdc85402f89ed1f there is no dependence
relationshop between create-packages and real-update-packages, which
results on the package building cluster in a race condition
real-update-packages tries to open a package which is being created by
the create-packages target and make the whole build fail.

Ensure create-packages and real-update-packages is sequential