--build=type
              Specifies  the  build  type  from  a  comma-separated  list   of
              components (since dpkg 1.18.5).  Passed to dpkg-genchanges.

              The allowed values are:

              source Builds  the  source package.  Note: when using this value
                     standalone and if what you want is simply  to  (re-)build
                     the source package, using dpkg-source is always better as
                     it  does  not  require  any  build  dependencies  to   be
                     installed to be able to call the clean target.