package/refpolicy: fix the configure, build and install steps

The refpolicy configure and build step were not correctly defined. The
configuration was split between the configure and build step, while
both the compilation and the installation were done in the install
step. Fix this by moving all the configuration within the
configuration step and by adding a call to make in the build step to
compile the policy.

Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>