HPCC-9097 Added plugins flag to file name on rpm based systems

Added WITH_PLUGINS variable that is used to determine if -with-plugins
is added to the rpm package name.

Signed-off-by: Philip Schwartz <philip.schwartz@lexisnexis.com>
Merge pull request #4327 from pschwartz/HPCC-9097-package-with-plugins

HPCC-9097 Added plugins flag to file name on rpm based systems

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>