Rename --dest-dir to --build-dir

``--build-dir`` is a more accurate name. ``--dest-dir`` seems to suggest
that this is where the packages ultimately end up. While it's true that
the packages do end up within that directory, they are copied to the
artifact directory, from which they are ultimately retrieved by the
jenkins master.
Add SRPM to build artifacts for automated RPM builds
Merge pull request #15731 from terminalmage/buildpackage-tweaks

Two tweaks to automated RPM builds