redhat: parallel builds

redhat: parallel builds

Parallel builds can be an order of magnitude faster. Add the
_smp_mflags macro to all invocations of make in the rpm spec,
to make use of all available cores and SMT threads on the build
system. This should also help noticing new dependency issues
early. Note the macro can be overridden on the rpmbuild command
line.

Reviewed-on: https://gerrit.openafs.org/13240
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit e60766286b7a581dcdd14466884ea7fdcae10918)

Change-Id: I3428e5acc7114a5bf1a1090352055041ef099fbd
Reviewed-on: https://gerrit.openafs.org/13249
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: Benjamin Kaduk <kaduk@mit.edu>