ci: install git and checkout using it

ci: install git and checkout using it

Atm the checkout action pulls the whole repo as tarball, since git is
missing. Since we install packages via local actions, we need to first
do an initial sparse checkout, install the packages (git including) and
do a proper second checkout.

At which point, the second checkout action claims to set safe.directory
(it's the default) although in practise we need to do it again. Perhaps
it's getting tripped by our initial sparse checkout?

Either way, explicitly set the option so that git just works.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/86
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>